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FILE NAME: Mine Safety Appliances (MSA) DATE: 0000 DOC#: MSA019 DOCUMENT DESCRIPTION: Book - Pertinent Questions & Answers Concerning Dusts 60Z0S0 OS % 00/ Foreword T h e r e is an increasingly wide and intense interest in harmful effects of breathing dusts, especially those that contain free silica and cause the disease of the lungs known as silicosis- Interest has been further stimulated by the work of Federal agencies and States in industrial hygiene, and by legislation that provides compensation for injury to health. A s a result; many persons in industry w ho are responsible for healthy working conditions have been confronted with the need of becoming acquainted with dust diseases, nature o f dust, its composition, size of particles, and the amount th a t is harmful, and the means for preventing exposure and protecting workmen. Much has been said and published on these subjects, but it has been presented in terminology and language of a specialized, technical, and scientific nature that is either meaningless to most persons or creates a good deal of misunderstanding. Also, considerable confusion has arisen from the conflicting opinions and views that have been widely expressed. In this booklet it is endeavored to present some of the questions that arise continually regarding the nature and effects of dusts, and to answer these questions in sample and insofar as possible non-technical language. SC 030710 Pertinent Questions and Answers Concerning Dusts 1. <3. What are th* usual dassificatians of air-carried particles? A. Air-carried particles are usually classified into three groups: 1-- Ousts 2-- Fumes 3--M ists 2. q. What are dust? A. Dusts are mechanically generated particles resulting from such opera tions as drilling, blasting, crushing, and handling o f rocks and minerals; sand-blasting; stone a n a granite cutting; grinding and polishing; and all similar operations and processes. The greater percentage of particles o f air carried dusts are below one micron in size with an average be tween 0.5-0.7 microns. 3. Q. W hat is a micron? A . A micron is a unit of measurement, one micron being equal to about 1/25.000 of an inch or m other wards it would require 25,000 particles each one micron in size laid end to end to measure one inch. 4. q. W hat Is the sm allo il partide that can b e soon by the naked eye? A. The smallest partide visible to a person with average eyesight is about 100 microns in dimension. This is 1/250 of an inch. S. Q How d ees this compare w ith the size o l the average partide b u n d in air-bom industrial dusts? A. This is one hundred and fifty to tw o hundred times the size of die average particle found in industrial atmospheres. In other wends, the particles of dust of significance from the standpoint of health are only a small fraction of the size th at is visible to the n a trd eye. 6. Q. W hat range of partide sixes is important? A. The panicles below 5 microns are o f most importance as dusts of larger size settle out of the air very quickly and are not likely to be breathed. In general the particles of dust found in industry are below one or two microns with as much as 50% below 0.5 or 0.7 micron. Under some conditions the size may be larger or smaller than this genera] size range. 7. Q. W hat arm fum ss? - A. Fumes are particles produced in chemical and metallurgical processes, welding, a id similar operations, or b y the decomposition of chemicals by heat and combustion. The average partide d ie is less than that of dusts. Most fumes have an average p a ra d e size of 0.2-0.3 microns. T he important harmful fumes are usually the fumes of metals or their compounds such as lead oxide, zoic oxide, and cadmium oxide. Owing to their small partide size, fumes are even more difficult to remove by filters than are mechanically generated dusts. 2 V V. *' \ * * Jr *** .* f * * / . *, */ * . * . \ , v / . vr.,.` 4 ' v ^ - 'k I 1'' - `t* *: , - V .** :: . * r . >* ' -: ` * . , * '4J . I ' k `| f-, ,*,i IV **V, *. VV;.T- -.t ; * *% %* * . s' ,,* . * w* 1*' *.- - V . * / :' ' , . a V- r s) : ______ 1. ' " * '* . * . * L. IQ 15 5 3 2 I j MICRONS SILICEOUS DUST FROM M INE AIR Magnified 100 n o ta The dstst p a m e la and dots shown in chis iQnsCncdon arc magnified 00 times their actual s a t. I f they were n o t magnified ro this extent all of the Brdeles and dots would be invisible, Even the largest or 10 micron sixe would be only one-tenth that which could be seen with che naked eye and the average partide uiould be lest than onehundredth the n o b le nee- T iro dlstseraus that the smallest porfele that can be seen with the na^ed eye is about 100 microns in dimension and th at all an a im e d dost is mumble. 8. Q. W hat are mists? A. Mists ire particles of liquids or mixtures of liquids and solids; in other words, wet particles. Their site depends upon the procea by which they were generated. Good examples o f mists are r the so-called "fogs" produced in spray coating w ith materials such as siliceous glares or paints chat contain lead, and the chromic acid mist produced during chromium plating. 9L Q . W h a t d u sta a r e d a n g e ro u s? . A. The effect of many industrial dusts on health is not known as yet since the physiological reactions of most dusta do not appear for some yearn, and the use o f many dust producing compounds is relatively hew. Most authorities agree that most dusts are harmful in son degree if breathed in sufficient concentration over a period of time. T h e safe course is to eliminate all dust down to the limits th at are considered good engineering practice in dust control. 10. Q . H ow a ro d u s ts classified in re la tio n to th e ir effects on h e a lth ? A. Dusts are usually classified into three groups: 1-- Toxic o r poisonous dusts. 2-- --Nuisance dusts. 3-- FibrcBis-producing dusts. SC 030712 IX. Q. W hat is a toxic dust? A. A toxic dust is usually considered to be die dust of a poisonous ma terial, such as Ired and arsenic or their compounds, that produces injury to organs such as the circulatory system, heart, liver, kidneys, brain, and nervous system. W hen a poisonous dust is inhaled and deposited in the lungs, it dissolves and is carried by the blood to all organs and tissues. It may also be deposited in die mouth and throat by inhalation or contamination with dirty hands, and later swallowed and enters the body through the digestive tract. 12. Q. What is a nuisance dust? ft. A nuisance dust is one that is often associated with an increase m respiratory diseases (such as, a d d s in the head, bronchitis, pneumonia, and tuberculosis). M any such dusts are discomforting and irritating to the worker and may be harm ful They do not produce toxic effects or foxm fibrous tissue in the lungs. 13. Q . W hat is a fibroma-producing dust? A. U is one that through its action in the lungs causes a disease of the normal lung tissue and a replacement of this vital tissue w ith fibrous (scar) tissue. 14. Q. What is pneum oconiosis? A . It is a term applied to any lung disease arising from inhalation of dust. 15. Q . W hat is sificoab? A- It is a disease o f the lungs in which die normal lung tissue is replaced by fibrous (scar) tissue due to breathing air th a t contains free silica dust (silicon dioxide. SiCte). 16. Q . Can silicosis lie produced b y any substance other than free silica? A . Silicosis ia a specific disease caused only by breathing free silica. How ever, there are indications that the presence of other kinds of dust and gases may influence the effect of silica in the lung. 17. Q. A. ' W hat is miners' pthisds? ' It is a term used frequently to designate a condition o f silicosis com plicated by the presence of tuberculosis. ' 18. Q . What is a nthraco-ailicosM (m iner's asthm a)? A. It is a chronic disease of the lungs in which the normal lung tissue is replaced by scar tissue caused by breathing excessive amounts of a mixture of silica dust along w ith coal dust. 19. Q . W hat is asb estos? A. It is a disease of the lungs in which the normal long tissue is replaced by fibrous (scar) tissue due to breathing air that contains asbestos dust. 4 SC 030713 20. Q . W hat are the principal factors in determ ining the hecdtb bastard {ram air-earned dust? A. The following factors are usually important: 1-- Chemical composition of the dust. 2--A m ount of dust in the air. 3-- Size of the dust particles. A-- Length of tune of exposure. 2L Q. W hat Is m eant by chem ical composition of a dust? A. All materials such as rocks and minerals are not what might be termed pure chemical compounds, but are mixtures o f several chemical com pounds. T he chemical composition is the kind and amounts of these var ious components. In the case o f alica-beanng substances, the amount of siUca present may vary from almost nothing to 100%. The amount of free silica present is obviously the important factor in the silicosis producing properties of a dust. 22. Q. Is the chem ical com position of the dust is the air the sam e a s the substance that is being drilled, handled, crushed, or processed? A. A s most dust producing substances dealt with in industry contain more than one mineral component, some of these components will crush or disintegrate more easily than others and thereby form a larger pro portion of small particles. These smaller particles will tend to pre dominate in the air while other constituents being larger will settle out. For this reason, the composition of the dust in die air may vary greatly from the composition of the rock o r mineral. 23. Q . W hat is d ie importan ce oi tb s chem ical com position oi a dust? A. T he chemical composition reveals the harmful constituents and their amount, and constitutes die basis far judging the harmful qualities of the d u st This information is an important factor along with con centration and time of exposure in determining the hazard. 24. Q . W hat are the important step s in determ ining the chem ical com position of a dust? A. It is necessary to first obtain a sample that represents the dust in the air breathed, and then subject the sample to methods of analysis that are known to give accurate results for the constituents desired. 25. Q . How pan a representative sam ple of the dust in the air breathed h e obtained? A. It can be obtained only by collecting the dust from the air. Samples o f pieces of rock o r settled dust do not necessarily hear any close re lation in composition to the dust floating in the air. 26. Q . How ca n a sam ple o i sufficient size for chem ical an alysis be collected from the ah? A. Collection from the a ir can be accomplished with dust collection devices such as the impinger, electrostatic precipitator or filter type of collectors. s SC 030714 27. Q . W hat m ethods a re g e n era lly u se d lor determ ination of the percent of b e e silica in dusts? A. 1-- By observing the action o f the small dust particles on light with the aid of a special type of microscope. T his is known as the petrographic method. 2-- By chemical analysis. 3-- By observing the action o f the panicles on X-Rays. 28. Q . W hat are the lim itatiana of th e petrographic m ethod? A. It is impossible by this method to examine individual particles below one o r two microns in size and since most of the air-earned dust is below this size range, one must rely on petrographic information obtained from particle sizes that are above those of primary significance. 23. Q . W hat are the lim itations of tile chem ical m ethod? A . There is no known chemical method that is specific for free silica (SiOs) when this constituent is present with silicates. However, by observing the difference in the rate a t which silica dissolves in certain adds as compared w ith other constituents a rough estimate can be obtained for some dusts, but w ith others the method will be greatly in error. 30. Q . W hat a re the Hmitatians of the X-Ray m ethod? A- T he X-Ray procedure can be used for making specific determinations o f free silica in a very small sample such as 25 to TO milligrams. The disadvantage of the method is that it requires very expensive ap paratus. 31. Q . W hat is m eant b y size of particle; how is il expressed? A . T he size of the particle is its largest dimension, usually expressed in microns. It has been stated by authorities that if ail dust below one micron in size could be eliminated, nearly all dust disease would be eliminated 32. Q - H aw can the size of dust particles b e determ ined? A . The sire of dust partides is measured by means of a microscope or by projection of the dust partides on a screen similar in general principle to ordinary lantern slide projection. T he partides as seen in the microscope o r projected are then measured. 3X Q . How quickly does fine dust settle? A . It settles very slowly. In the table given below will be found the time in minutes estimated for silica dust o f given sizes to fall one foot in stilt air. ' Size in microns Time in minutes to fall one foot 'A '/t 1 r 2 5 590. 187. 54. 14.4 2.5 6 J 34. 0 - D oes absence af visible dust m ean absence at fine dust? A . No. The operation may produce only fine dust or the viable dust may have disappeared owing to its rapid rate of seeding, leaving the invisible but harmful dust in the air. 35. Q . W hat is m eant by dost concentration: how is it expressed? A . The concentration is the amount of dust suspended in a given volume of air. It is usually expressed in number of particles in a cubic foot o f air, or millions o f particles in a cubic meter of air, o r in a cubic centimeter It may also be expressed as th e weight of dust in a given volume of air as milligrams in a cubic meter o r grams in a cubic foot. 36. Q. W hat is the relation am ong these units of quantity? A. Number of cubic feet times .02832 gives number of cubic meters (m 3). Number of cubic meters times 35.31 gives number o f cubic feet. Number of cubic feet times 28,317 gives number of cubic centi meters (cc.) , Number of milligrams times .001 gives cumber of grams. Number of grains times 54.80 gives number o f milligrams. Number of grains tunes .00229 gives ounces (aveerdupois). 37. Q , How con tho concentration in particles per cubic centim eter be converted to number of partidea per cubic foot? A. M ultiply the number of particles pci cubic centimeter by a million and'divide by 35.31 to get number of particles per cubic foot 38. Q . How many particles of car-cam ed dust are in one nuUigram w eight of dust? A. I t has been found th a t one milligram of silica dust of the site range present in industrial atmospheres contains about 200 to 300 million particles. 39. Q. What apparatus and methods are generally used for determin in g duet concentrations? A. The impinger and electrostatic precipitator are the instruments general' ly used for this purpose. Details of the instruments and methods can be found in publications of die United States Bureau of Mines and the United States Public Health Service. i \ i 40. Q . W hat is an impinger? t A . It is a device by which air is draw n at a definite rate of flow and at \ high velocity through a small n o u le so directed as to strike the bottom of a glass flask which is partially filled w ith a liquid such as water, alcohol, o r a mixture of these liquids. T his high velocity action causes the dust particles to be "wetted" and retained in the liquid. Seme of this liquid is then examined under a microscope and a count o f the } dust particles present is made. 7 SC 030716 41. Q . W a tt is an electros tatic precipitator? A. it< a device by which air is drawn a t a definite rate of flow through a high voltage electrical field so arranged as to cause any dust to be re moved and deposited in a sampling Cube. The dust collected can be determined either by counting die number of particles w ith a micro scope or by weighing. It is an efficient method but requires a source o f electrical energy. As with the impinger, the electrostatic precipitator collects the dust continuously from a comparatively large volume o f air and thus provides a sample that represents average conditions. It may even be used to collect a sample that is large enough for chemical analysis. 42. Q. R ow cent exposure be determined? A. Since exposure is a term that involves concentration, particle site, chemical composition, and duration of tame, it is necessary to determine all of these in order to properly evaluate the degree and extent of exposure. Tim time dem ent requires an accurate ;ob analysis in which is recorded the amount of time spent by a workman at his various operations. This record should then be associated with the dust con centration, particle site, and chemical composition of the dust a t each operation and the average over all daily exposure determined. For Example: Summary of Dust Exposure of Leyner Dnllers in a Granite Quarry Activity Average exposure in mtltions of partides pear cubic foot. Hours spent in each activity Particle hrs. (millions per cubic foot) D rillin g __________ .._ Changing drills.-- ... W atching dnils...... ... Broaching.------------Blowing off holes,- ._ 213.4 9.8 8.0 6.0 1085.0 4 853.6 I 9.8 2 16.0 34 4.5 271.3 T o ta l....................... ... ' 8 1155.2 1175.2 particle hours in millions per cubic foot 144.4 million particles per - . cubic foot. Average expos- 8 " ure throughout the day. Table from U . S. Public Health Bulletin 217 by Bloomfield and Dailavalle 43. Q . W hat is a reepirator? A. Any personal protective device designed to prevent the wearer from inhaling the harmful constituents m his surrounding atmosphere is called a respirator. 8 SC 030717 44. Q. How ore the various typ es ol respirators usually classified? A . Respirators are classified as follows: 1. Air-supplied respirators. 2. Chemical filter respirators. 3. Mechanical filter respirators. 45. Q . W hat is a suppH eddr or air-line respirator? A . It is essentially a hose line through which air that is safe to breathe is conveyed to a facepiece worn by the workman. Air-line respirators are approved by the United States Bureau of M ines under schedule No. 19 The air may be supplied from the compressed air line although pre ferably it should come from a separate blower unit designed to furnish air free from distasteful or harmful trapunties. 46. Q. W hat harmful or objectionable constituents m ight b e present in high pressure cur as produced by an ordinary reciprocating type of compressor? A . A ir from this source may contain oil odors, mists o f oil or water, particles o f rust or dirt from the air receiver o r air lines, and in case of improper compressor operation there may be burning of the lubri cants w ith the formation o f carbon monoxide. 47. Q. W hat precautions should b e taken to lessen the danger from air co ntamin ation in the u se of reciprocating type of air com pres sors? A . Good maintenance and care in operation of die compressor, tempera ture indicators on the outlet sick of compressor, and carbon monoxide detecting equipment or carbon monoxide alarms on the o udet side to give indication o f the presence of any carbon monoxide. Individual compressor units so constructed as to make generation of harmful gases impossible are desirable sources o f clean air for-air-line respirators 48. Q. W hat is an abrasive mask? A. A n abrasive mask is essentially an air line respirator with a special hood for protection against high velocity particles in sand or shot blasting operations. 43. Q . W hat is a chem ical filter respirator? A . It is a respirator designed for removing gaseous constituents from die air breathed. The filtering materials in these respirators are usually granules that react w ith the harmful constituents and remove them. Chemical filter respirators are approved against light concentrations of organic vapors under U. S. Bureau of Mines schedule No. 23. 50. Q . W hat is a m echanical filter respirator? A. A mechanical filter respirator is a device that removes by mechanical filtration the particles of harmful constituents from air th at passes through it. These devices include dust, nust, and fume respirators. Each o f these types of mechanical filter respirators is designed to protect the w earer against the particular kind of m atter to be dealt with. 9 W SSI 51. Q. What is a United States Bureau a i M ines '"approved" mechani cal filter respirator? A. It is a respirator that has officially passed the rigid test requirements of the United States Bureau of Mines is outlined in that Bureau's Ap proval Schedule No. 21. 52. Q. What or United S tales Bureau of M ines schedules No. 19, 21 and 23? A. They are publications that describe the requirements and tests that respirators must meet in order to obtain the approval of the Bureau of Mines. Free copies of these publications may be obtained upon request from the United States Bureau of Mines, Washington, D. C. 53. Q. Who makes the approval tests? . A. The Bureau of Mines makes the tests at its Pittsburgh Experiment Station where experienced personnel and complete laboratory facilities for dust investigations are available. 54. Q. For what types ai mechanica l filter respirators does the Bureau of Mines schedule No. 21 provide approval requirements? A. Schedule No. 21 provides approval requirements for mechanical filter respirators for protection against mechanicilly generated dusts; fumes of various metals; and mists such as those from chromic and and from spray coating in the absence of harmful vapors and gases. Combi' nations of these types may also be approved. 55. Q. What are the general performance requirements that a m echan ical filter dust respirator must give in order to obtain th e ap proval of the Bureau ci Mines? A. The general features of the performance requirements are: 1-- D ust'tight fit of the facepiece. 2-- Reduction of dust in the inhaled air below an amount that causes harm. 3-- A resistance to breathing that is below that which produces discomfort. 4-- A satisfactory degree of convenience, durability, and service, 56. Q . What is the (rise o i the dust partides used by the United States Bureau of M ines in the approval tests ol m echanical filter respirators? A. The dust particles used in the tests are 91% below 1.78 microns and 70% below 0.6 micron. These size characteristics are very similar to those found in the atmospheres of mines and-industrial plants. 57. Q . What severe dust filtering and resistance performance must a m echanical filter dust respirator give to pass the approval test? A . A ir that contains fifty milligrams per cubic meter (approximately 300 to 500 million partides per cubic foot) of dust of die small c"* 10 SC 030719 specified by th e Bureau of Mines is drawn through the respirator at a rate of 32 liters a minute, or at approximately the rate a t which air is breached by an average man doing work. 'Hie total amount of dust that leaks through the respirator in. a 90 minute test period during which 2.88 cubic meters or 100 cubic feet of air are passed must not exceed 3.0 milligrams o r 0.0001 ounces. The resistance to inhalation when tested w ith air flowing through the respirator at 8 f liters a minute must at no time exceed 2 inches of water column. This resis tance is below th at which causes discomfort. 58. Q. Are the Bureau of M ines approva l requirem ents unnecessarily exacting and im practical? A. No- The approval requirements represent the minimum protection that a respirator should give m order to protect the wearer adequately 59. Q . Whcrt are the most important features oi a respirator? A. I---Adequate respiratory protection. 2-- Com fort and convenience. 3-- Ease and cost of maintenance. 60. Q. What is meant by the efficiency a i a respirator: and what test (acts concerning efficiency must b e known to determ ine if a respirator gives adequate protection? A . The efficiency of a respirator is the percentage o f the dust in the air that is retained on the filter. A t least three very important facts should be known in order to determine if a respirator, that las a reported high efficiency, also gives adequate protection: 1-- The dust concentration used in determining the efficiency figure. 2-- T h at the particle size of the dust used m determining the efficien cy represents the size of the dusts found in industrial atmospheres. 3-- T har the percentage inefficiency, or the amount o f dust that leaks through, does not exceed that which is safe to breathe. 61. Q . How d oes variation in particle size effect the reliability of an efficiency valu e o i a respirator? A. The statem ent th at a respirator is 98% efficient means little if the particle size range o f the dust tested is not given because the difficulty in removing dust increases as the particle size decirases so that dusts below 1 to 2 microns are much more difficult to remove than the larger sizes, yet it is p a rtic le below 1 to 2 microns th at predominate tn in dustrial and mine atmospheres and produce the harmful effects. A respirator which would cot effectively remove dust below 2 microns oould be 98% efficient provided the test was made against concentra tions that contain only a small amount of parades below 2 microns in site. . ti SC 030720 62. Q . How is tho reliability of an efficiency value as a m easure of dust protection affected b y the concentration of dust in the air? A . A respirator may have high percentage efficiency and still leak enough dust through che filter to cause barm. Far example, a respirator that is 97% efficient against a concentration of 700 million parades of dust per cubic foot of air (a not unusual case) would leak 15 million parades which is more than is considered a permissible amount of dust with a high'silica content in the air breathed. The Bureau of Mines approval is given only to respirators th a t do not leak enough dust to bring the dust in dm air breathed above permissible limits. S3. Q . W hat is m eant by comfort and convenience? A . The following factors are elements of comfort and convenience: 1-- Resistance to breathing. 2-- Degree of impediment and encumbrance to vision and normal performance of work. 64. Q . Should comfort and protection b e considered separately? A. No. A ny acceptable respirator must give both adequate protection and an acceptable degree of comfort. 65. Q. W hat is meant by cost of m aintenance? A. T he cost o f maintenance is the expense involved in keeping the respira tor in an efficient, comfortable, and clean working condition. Low cost of replacement of fibers is an important element in this expense. 66. Q . W hat is m aanl b y sa so a f m aintenance? A. By ease of maintenance is meant the ease with which a dust laden respirator can be restored to its initial high degree o f efficiency and comfort through: t--Servicing. 2-- Replacement of filters. 3-- Sterilization- 67. Q . How cun respirators bo sterilized? A . Scrub rubber and metal parts with soap and water. Rinse in warm water and immerse for 10 minutes in a solution of formalin made by placing one part of 40% formaldehyde solution into 9 parts of water. Instead of the formalin solution, l part of carbolic acid in 33 parts of water, or 1 p art of Lysnl in 50 parts of water, or 8 parts of denatured alcohol in 3 parts of water may be used. All respirators should be thoroughly rinsed with w ater immediately after immersion in the sterilizing solution and put in a clean place to dry. 12 Mechanical Filter Respiracors For Protection from Dusts, Mists and Fumes Manufactured by Mine Safety Appliances Company M i.A . "C O M P C ' DUST RESPIRATOR W ith "C om fo" Cushion Facepiece M .& A "CLEAR-VUE" DUSTFOE RESPIRATOR SC 030722 Air Line Respirator Equipment Manufactured by Miae Safety Appliances Company M-S.A- AIR LINE RESPIRATOR W ith "Com fo" Cushion Facepiece M.S.A. ABRASIVE MASK SC 030723 1 1 Accessory Equipment for Air Line Respirators Manttfdtmred by Mine Safety Appliances Company Entirely self-contained and readily portable. ib e unit removes oil mots, oil vapors, water, and ptpe scale from compressed air and provides effective protection against excessive and variable pressures in the air supply. It is dcgncd (or attachment Co the mam compressed air lines and ha a capacity of one to six take-off lines to >uppUed air masks and respirators. The M S A. Portable Air Filter and Regulator is equipped with a chemical 5 611 for efficient removal of odors and vapors and a mechanical separator which removes oil, water and dire from incoming compressed air A built-in M.S.A. PORTABLE AIR FILTER pressure regulator governs air pressure AND REGULATOR at x predetermined safe !mut. I i \ i M S .A . CleanAir Blowers wash. cool, and if humidify the atr they supply--by utilising a small, constant flow of water through the rotor chamber. The water also acts as a com i pression seal, eliminating all metal-to m etal contact. Since ito lubrication is necessary for the operation of CkatiAu- Blowers, no oil or grease comes in contact w ith delivered air i No auxiliary air Alter o r regulator a neces i & sary with a CleanAir Blower. M S A . CLEANAIR BLOWER M .3 A CleanAir Blowers are furnished in a wide range of Aces to meet desired respi ratory requirements. 15 SC 030724 Air Sampling Equipment for Dusts, Mists and Fumes Manufactured by Mine Safety Appliances Company M.S.A. M IDGET IMPINGER The M .SA . Midget Imptager spies at a rate of oae-tenth o f a cubic foot per snout* and is operated by a hand-cranked, positive' acting 4 cylinder pump of ingenious design. This pump, in con/unction with a vacuum regulator, maintains an unfluctuating suction regardless of minor variations m the rate or smoothness of cranking. The apparatus is contamed *n a compact, sturdy carrying case complete with nine calibrated glass sampling tabes. The light weight, >roall dimensions, ad almost effortless operation ot this modern instrument greatly broaden the field of dust sampling by the tmpinger method. Isolated locations, confined spaces, lack o f electric cur' rent or compressed air presents no barriers to the M.S.A. M idget Impmger. M.S.A. ELECTROSTATIC Dust aad Fume Sampler This instrument, designed for quantitative sampling of dust, fume, and mist, employs the principle of presonuattofi w ith electrostatic precipitation. The unit is compact and ea*y to use for sampling from the general atmos phere or from **acks or ducts: it is the only efficient sampler for fumes, particularly lead fumes Other feature are large sampling volume of l cu. ft. per minute permitting accurate determinations of very low concentrations of atmospheric particulate matter; flow measure ment with orifice and mechanical manometer -- no liquids to spilt; extension tube for <>ampling a t breathing level with apparatus on the floor; and coflection of samples in a special aluminum tube permitting determina tions by weight, count or chemical analysis. This precipitator operates on 110-120 volts, 60 cycle, alternating current. Case dunerv Muns are 16 x U l4 x 10V4 inches. 16 Print#* To U S.A. SC 030725 ! PERTINENT QUESTIONS and ANSWERS CONCERNING DUSTS it i ii i I MINE SA FET Y APPLIANCES CO. Ruddock, Thomas and Mesde Streets . PITTSBURGH 8, PA. SC 030726 Foreword ' h ERE is an increasingly wide and intense interest in harmful effects of breathing dusts, especially those that contain free silica and cause the disease of the lungs known ,ts silicosis. Interest has been further stimulated 'Vf the work of Federal agencies and States in industrial hygiene, and by legislation th at provides compensation for injury to health. As a result many persons in industry who are responsible for healthy working conditions have been confronted with the need of becoming acquainted with dust diseases, nature of dust, its composition, site of particles, and the amount that is harmful, and the means for preventing exposure and protecting workmen. Much has been said and published on these subjects, but it has been presented in terminology and language of a specialized, technical, and scier,life nature that is either meaningless to most persons or creates a good deal of misunderstanding. Also, considerable confusion has arisen from the conflicting opinions and views th a t have been widely expressed. In this booklet it is endeavored to present some of the questions that arise continually regarding the nature and effects of dusts, and to answer these questions in simple and insofar as possible non-technical language. Pertinent Questions and Answers Concerning Dusts 1. Q . W h a t a r e th e u s u a l clas s lfica tion s of a ir-c a rrie d particles? A, Air-carried particles arc usually classified into three groups: 1-- Dusts 2-- Fumes 3-- Mists 2. Q. W hat a re dusts? A. Dusts are mechanically generated parades resulang from such opera tions as drilling, blasting, crushing, and handling of rocks and minerals: sand-blasting; stone and granite cutting; grinding and polishing; and all similar operations and processes. The greater percentage of parades of air carried dusts are below one micron in site with an average be tween O.f-O.7 microns. 3. Q . W h a t is a m icron? A. A micron is a um t of measurement, one micron being equal to about 1/25,000 of an inch o r in other words it would require 25,000 parades each one micron in sire laid end to end to measure one inch. 4. Q . W h a t is th e sm a lle st p a rtic le th a t c a n b e s e e n b y th e n a k e d ey e? A. The smallest particle visible to a person with average eyesight is about 100 microns in dimension. This is 1/250 of an inch. 5. Q . H ow d o e s thin c o m p a re w ith th e size of th e a v e ra g e particle found in air-horn industrial dusts? A . This is one hundred and fifty to tw o hundred times the size of the average partid e found in industrial atmospheres. In other words, the parades of dust of significance from the standpoint o f health are only a small fraction of the size that is visible to the naked eye. 6. Q . W h a t r a n g e of p a r tid e sizes is im p o rtan t? A. The parades below 5 microns are of most importance as dusts o f larger size settle out of the air very quickly and are not likely to be breathed. In general the particles of dust found in industry are below one or two microns with as much as 50% below 0.5 or 0.7 micron. U nder some conditions the size toay be larger or smaller than this genera! size range 7. Q . W hat a re fumes? A. Fumes are particles produced in chemical and metallurgical processes, welding, and similar operations, o r by the decomposition of chemicals by heat and combusaon. The average p a rad e size is less than that of dusts. Most fumes have an average partid e size of 0.2-0.3 microns. The important harmful fumes are usually the fumes of metals o r their compounds such as lead oxide, zinc oxide, and cadmium oxide. Owing to their small p a rad e size, fumes are even more difficult to remove by filters than are mechanically generated dusts. Cnmryof V. i, *UrU9fMlftH ID 15 5 3 2 MICRONS I S SILICEOUS DUST FROM M INE AIR Magnified 100 times The dust piracies and do a tkow n in this tHiwtratipu use magnified 100 tuxes their actual su e. If they were not raagnipcd to this extent all of the particles and dots lUDisId he muinidc. Even the largest or 10 micron use would he only one'lench that which could he teen with the na^ed eye and the average particle would he less than onehundredth the visible rise. This illustrates th at the smallest particle that can he seen with the na^ed eye is about ICO microns m dimeitnou and that all air corned dust is invisible. B. Q. What cae mists? A. Mists are particles of liquids or mixtures of liquids and solids; in other word, wet particles. T heir size depends upon the process by which they were generated. G ood examples of mists are: the so-called " fogs" produced in spray coating with materials such as siliceous glazes or paints that contain lead, and die chromic ad d mist produced during chromium plating. 9, Q. What dusts are dangerous? A. T he effect of m any industrial dusts on health is not known as yet since the physiological reactions of most dusts do not appear for some years, and the use of many dust producing compounds is relatively new. M ost authorities agree th at most dusts are harmful in some degree if breathed in sufficient concentration over a period of time. T he safe course is to eliminate all dust down co the limits th at are considered good engineering practice in dust control. 10. Q. How are dusts classified is relation to their effects on health? A. Dusts are usually classified into three groups: 1-- Toxic or poisonous dusts. 2-- Nuisance dusts. 3-- Fibrosis-producing dusts. 5 SC 030729 H . Q . W hat is a toxic dust? A_ A toxic dust is usually considered to be the dust of a poisonous ma terial, such as lead and arsenic or their compounds, that produces injury to organs such as the circulatory system, heart, liver, kidneys, brain, and nervous system. W hen a poisonous dust is inhaled and deposited m the lungs, it dissolves and is carried by the blood to all organs and tissues. It may also be deposited m die mouth and throat by inhalation or contamination w ith dirty hands, and later swallowed and enters the body through the digestive tract. 12. Q- W h a t is a n u isa n c e d u st? A. A nuisance dust is one that is often associated with an increase ui respiratory diseases (such as, colds in the head, bronchitis, pneumonia, and tuberculosis) M any such dusts are discomforting and irritating to the worker and may be harmful. They do not produce toxic effects or form fibrous tissue tn the lungs. 13. Q. W h a t is a fib ro sis-p ro d u cin g d u st? A. It is one th at through its action in the lungs causes a disease of the normal lung tissue and a replacement of this vital tissue w ith fibrous (scar) tissue. 14. Q. W h at is p neum oconiosis? A. It is a term applied to any lung disease arising from inhalation of dust. 15. Q . W h a t is silicosis? A. It is a disease of the lungs m which the normal lung tissue is replaced by fibrous (scar) tissue due to breathing air that contains free silica dust (silicon dioxide, S iO :). ! 16. Q. C a n silicosis b e p ro d u c e d b y a n y s u b s ta n c e o th e r th a n free silica? . A. Silicosis is a specific disease caused only by breathing free silica. How ever, there are indications that the presence of other kinds of dust and gases may influence d ie effect of silica in the lung. I i 17. Q- W h a t is m in ere' pthisis? i A. It is a term used frequently to designate a condition of silicosis com j plicated by the presence o f tuberculosis. 18. Q- W h a t is anihraco-m H cosis (a im e r's asthm a}? A. It is a chronic disease of die lungs in which the normal lung tissue is replaced by g-m- tissue caused b y breathing excessive amounts of a i mixture of silica dust along with coal dust. 19. Q- W hoi is asbusloaia? A. It is a disease of the lungs in which the normal lung tissue is replaced by fibrous (scar) tissue due to breathing air th a t contains asbestos d u st SC 030730 20. Q. W h a t a r e th e p rin cip al {actors in d e te rm in in g th e h e a lth h a z a rd h am air-carried dust? A. T he following factors are usually important: I-- Chemical composition of the dust ?--Am ount of dust in the air. 3-- Size of the dust particles 4-- Length of time of exposure 21. Q. W h a t is m e a n t b y chem ical com position o i a d u st? A. A ll materials such as rocks and minerals are not what might be termed pure chemical compounds, but are mixtures of several chemical com pounds. T he chemical composition is the kind and amounts of these var ious components. In the case of silica-bearing substances, the amount of silica present may vary from almost nothing to 100%. The amount of free silica present is obviously the important factor in the silicosis producing properties of a dust. 22. Q. Is th e c h e m ic a l com position of the d u st in th e a ir th e s a m e a s th e sub stan ce that is being drilled, handled, crashed, o r processed? A . A s most dust producing substances dealt with in industry contain more than one mineral component, some o f these components will crush or disintegrate more easily than others and thereby form a larger pro portion of small partides. These smaller particles will tend to pre dominate in the air while other constituents being larger will settle out. For this reason, the composition of the dust in the air may vary greatly from the composition of the rock or mineral. 23. Q . W hat is the im portance oi the chem ical com position of a dost? A. T he chemical composition reveals the harmful constituents and their amount, and constitutes the basis for judging the harmful qualities of the dust This information is an important factor along with con centration and time of exposure in determining the hazard. 24. Q. W hat a re th e im portant steps in determ ining the chem ical com position of a dust? A . It is necessary to first obtain a sample that represents die dust in the air breathed, and then subject the sample to methods of analysis that are known to give accurate results for the constituents desired. 25. Q. H ow con a representative sam ple of the dust in the air breathed be obtained? A . It can be obtained only by collecting the dust from the air. Samples of pieces of rock or settled dust do not necessarily bear any dose re lation in composition to the dust floating in the air. 2B. Q. H o w c a n a sa m p le o i sufficient size for c h em ical a n a ly sis b e collected from the air? A. Collection from the air can be accomplished with dust collection devices such as th e impinger, electrostatic precipitator o r filter type of collectors. 27. Q . What m ethods are generally used ior determination ol the percent o i tree silica in dusts? A . !-- By observing the action of the small dust particles on light with the aid of a speaai type of microscope. This is known as the petrographic method. 2-- By chemical analysis. 3-- By observing the action of die particles on X-Rays. 28. Q . W hat are the lim itations of the petrographic method? A, It is impossible by this method to examine individual particles below one or two microns in sice and since most of die air-earned dust is below this size range, one must rely on petrographic information obtained from particle sizes that are above those of primary significance. 29. Q. W hat are the lim itations of the chem ical method? A. There is no known chemical method th at is specific for free silica (SiOs) when this constituent is present with silicates However, by observing the difference in the rate at which silica dissolves in certain adds as compared with other constituents a rough estimate can be obtained for some dusts, but with others the method will he greatly in error. 30. Q . W hat are the lim itations af the X-Ray method? A- The X-Ray procedure can be used for making specific determinations of free silica in a very small sample such as 23 to 50 milligrams The disadvantage of the method is that it requires very expensive ap paratus. 31. Q. W hat is meant by size of particle: how is it expressed? A . The size o f the particle is its largest dimension, usually expressed in microns, f t h ts been stated by authorities that if all dust below one micron in size could he eliminated, nearly all dust disease would be eliminated. 32. Q. How can d ie size of dust particles b e determined? A. T he size of dust particles is measured by means of a microscope or by projection of the dust particles on a screen similar in general principle to ordinary lantern slide projection. The particles as seen m the microscope or projected are then measured 33. Q. How quickly does fine dust settle? A. It settles very slowly. In die table given below will be found the time in minutes estimated for ulica dust o f given sizes to fall one foot in still air. Time in minutes to Size in microns fall one foot 590 Vz 187. l 54. 2 14.4 % 2.T 6 SC 030732 ' \ \ \ 34. Q. D oss absence of visible dust m ean absence of fine dust? A. No. The operation may produce only fine dust or the visible dust may have disappeared owing to its rapid rate of settling, leaving the invisible but harmful dust in die ait. 35. Q. W hat is m eant by dust concentration; how is it expressed? A . The concentration is the amount of dust suspended in a given volume of air. It is usually expressed in number of particles in a cubic foot of air, or millions of parades in a cubic meter of air, or in a cubic centimeter. It may also be expressed as the weight of dusc in a given volume of air as milligrams in a cubic meter or grains in a cubic foot. 36. Q . W hat is the relatio n a m o n g these units of quantity? A . Number o f cubic feet times .02832 gives number of euKc meters (m3). Number of cubic meters ames 35.31 gives number of cubic feet. Num ber of cubic feet times 28,317 gives number of cubic centi meters (cc.) Number of milligrams times .001 gives number o f grama Num ber of grains times 64.80 gives number of milligrams Number of grains ames .00229 gives ounces (avoirdupois). 37. Q . H ow c a n th e c o n ce n tra tio n in p a rth d e s p e r c u b ic centim eter be converted to num ber of particles per cubic loot? A . M ultiply the number of particles per cubic centimeter by a million and divide by 35.31 to get number of particles per cubic foot. 38. Q . H ow m an y particles of a ir-carried d u st a re in one nnUigTam w eight of dust? A . It has been found that one milligram of silica dust of the size range present in industrial atmospheres contains about 200 to 300 million particles. 39. Q. W hat ap p aratu s an d m ethods a re generally used for determ in ing dust concentrations? A. The impinger and electrostatic predpitator are the instruments general ly used for this purpose. Details of the instruments and methods can be found in publications o f the U nited States Bureau of Mines and the U nited States Public Health Service. 40. Q. W hat is an impinger? A . It is a device by which air is draw n at a definite rate of flow and at high velocity through a small nozzle so directed as to strike the bottom of a glass flask which is partially filled with a liquid such as water, alcohol, or a mixture of these liquids. This high velocity action causes the dust particles to be "w etted" and retained in the liquid. Some o f this Liquid is then examined under a microscope and a count of the dust particles present is made. SC 030733 41. Q. W hat is an electrostatic precipitator? A . It's a device by which air is draw n at a definite rate o f flow through a high voltage electrical field so arranged as to cause any dust to be re moved and deposited in a sampling tube. The dust collected can be determined either by counting the number of particles w ith a micro scope or by weighing. It is an efficient method but requires a source of electoral energy. As w ith the impinger. the electrostatic precipitator collects the dust continuously from a comparatively large volume of air and thus provides a sample that represents average conditions. It may even be used to collect a sample that is large enough for chemical analysis. 42. Q . H ow c a n e x p o su re b e d e te rm in e d ? ft. Since exposure is a term that involves concentration, particle size, chemical composition, and duration of time, it is necessary to determine all of these in order to properly evaluate the degree and extent of exposure. The time element requires an accurate job analysis in which is recorded the amount of time spent by a workman at his various operations. This record should then be associated with the dust con centration, particle sue, and chemical composition o f the dust at each operation and the average over all daily exposure determined. Tiff Example: Summary of Dust Exposure of Leyner Drillers in a Granite Quarry Activity Average exposure in millions o f particles per cubic foot. Hours spent in each activity Particle his. (millions per cubic foot) Drilling____________ Changing drills.____ W atdiing d rills......... Broaching._________ Blowing off holes...... 213.4 9.8 8.0 60 1085.0 4 853.6 l 9.8 2 16.0 Y\ 4.5 Yi 271.3 T otal.......... .............._.. 8 1155.2 1155.2 particle hours in millions per cubic foot 144.4 million particles per --------------------------- ~ T ------------------------------- cubic foot. A verage expos- 8 hr' ure throughout the day. Table from U. S. Public Health Bulletin 217 by Bloomfield and Dallavalle ii 43. Q . W hat is a respirator? i A. A n y personal protective device designed to prevent the wearer from i inhaling the harmful constituents in his surrounding atmosphere is called a respirator. 1 i SC 030734 44. Q. How are the various types oi respirators usually classified? A. Respirators are classified as follows: L. Air-supplied respirators. 2. Chemical filter respirators. 5. Mechanical filter respirators. 45. Q. W hat Is a suppfied-edr or air-line respirator? A. It is essentially a hose line through -which air that is safe to breathe is conveyed to a facepiece worn by the workman. Air-line respirators arc approved by the United States Bureau of Mines under schedule N o 19 The air may be supplied from the compressed air line although pre ferably it should come from a separate blower unit designed to furnish air free from distasteful or harmful impurities 46. Q. W hat harmful or objectionable constituents might be present in high pressure air as produced by a n ordinary reciprocating type of compressor? A. A ir from this source may contain oil odors, mists of oil or water, particles of rust or d irt from the air receiver or air lines, and in case of improper compressor operation there may be burning of the lubncants with the formation of carbon monoxide. 47. Q. W hat precautions should be taken to lessen the danger from air contam ination in the u se of reciprocating type of air compres sors? A. Good maintenance and care in operation of the compressor, tempera ture indicators on the outlet side of compressor, and carbon monoxide detecting equipment or carbon monoxide alarms on the outlet side to give indication of the presence of any carbon monoxide. Individual compressor units so constructed as to make generation o f harmful gases impossible are desirable sources o f clean air for air-line respirators 48. <3. W hat is an abrasive mash? A. A n abrasive mask is essentially an air line respirator with a special hoed for protection against high velocity particles in sand o r shot blasting operations. 49. Q . W hat 1b a chem ical filter respirator? A . It is a respirator designed for removing gaseous constituents from the air breathed. The filtering materials in these respirators are usually granules that react w ith the harmful constituents and remove them. Chemical filter respirators are approved against light concentrations of organic vapors under U. S. Bureau of Mines schedule N o 23. SO. Q. W hat is a m echanical filter respirator? A. A mechanical filter respirator is a device th at removes by mechanical filtration die particles of harmful constituents from air that passes through it. These devices include dust, mist, and fume respirators. Each o f these types of mechanical filter respirators is designed to protect the wearer against the particular kind of matter to be dealt with. 1 SC 030735 51. Q . W hat is a United States Bureau of M ines "approved" m echani cal filter respirator? A . It is a respirator that has officially passed the rigid test requirements of the United States Bureau of Mines as outlined in th a t Bureau s A p proval Schedule No. 21. 52. Q . W hat are United States Bureau oi M ines schedules No. 19, 21 and 23? A. They are publications that describe the requirements and tests that respirators must meet in order to obtain the approval of the Bureau of Mines. Free copies of these publications may be obtained upon request from the United States Bureau of Mines. W ashington, D. C. 53. Q. Who m akes the appraved tests? A. The Bureau of Mines makes the tests a t its Pittsburgh Experiment Station where experienced personnel and complete laboratory facilities for dust investigations are available. 54. Q. For w hat types of m echanical filter respirators d oes the Bureau of M ines schedule No. 21 provide approval requirem ents? A. Schedule No. 2L provides approval requirements for mechanical filter respirators for protection against mechanically generated dusts: fumes of various metals; and mists such as those from chromic acid and from spray coating in the absence of harmful vapors and gases. Combi nations of these types may also be approved. 55. Q- W hat are file general performance requirem ents that a m echan ica l filter dust respirator m ust give in order to obtain the ap proval of the Bureau of M ines? . A. The general features of the performance requirements are: 1-- Dust-tight fit of the facepiece. JI:' 2-- Reduction o f dust in the inhaled air below an amount that causes harm. 2--A resistance to breathing that is below th at which produces discomfort. A-- A satisfactory degree of convenience, durability, and service. 56. Q. W hat is the size of fits dust particles used by the United States Bureau of M ines in the a pprova l tests af m echanical filter respirators? A . H ie dust particles used in the tests are 95% below 1.78 microns and 50% below 0.6 micron. These site characteristics are very similar to those found in the atmospheres o f mines and industrial plants. 57. Q . W hat severe dust filtering and resistance perform ance m ust a m echanical filter dust respirator give to pang the approval test? A. A ir that contains fifty milligrams per cubic meter (approximately 300 to 500 million particles per cubic foot) of dust of the small sir; 10 SC 030736 specified by the Bureau of Mines is drawn through the respirator at a rate of 32 liters a minute, or at approximately the rate a t which air is breathed by an average man doing work. The total amount o f dust that leaks through the respirator in a 90 minute test period during which 2.88 cubic meters or 100 cubic feet of air are passed must not exceed 3.0 milligrams or 0.0001 ounces. T he resistance to inhalation when tested with air flowing through the respirator at 85 liters a minute must at no time exceed 2 inches of water column T his resis tance is below that which causes discomfort 58. Q. Ara the Bureau af M ines approval requirements unnecessarily exacting and unpractical? A. No. The approval requirements represent the minimum protection that a respirator should give in order to protect the wearer adequately 59. Q. W hat are the most important features of a respirator? A. 1--Adequate respiratory protection. 2-- Comfort and convenience. 3-- Ease and cost of maintenance. 80. Q. What is meant by the efficiency of a respirator; and w hat test facts concerning efficiency must b e known to determine if a respirator gives adequate protection? A. T he efficiency of a respirator is the percentage of die dust in the air that is retained on die filter A t least three very important facts should be known in order to determine if a respirator, that has a reported high efficiency, also gives adequate protection: 1-- The dust concentration used m determining the efficiency figure. 2-- T hat the particle site of the dust used in determining the efficien cy represents the size of the dusts found in industrial atmospheres. 3-- T h at the percentage inefficiency, or the amount of dust that leaks through, does not exceed that which is safe to breathe. SI. Q. How does variation in particle size effect the reliability of an efficiency value of a respirator? A. T he statement that a respirator is 98% efficient means little if the particle size range of the dust tested is nor given because the difficulty in removing dust increases as the particle size decreases so that dusts below 1 to 2 microns are much more difficult to remove than the larger sizes, yec it is partides below l to 2 microns that predominate in in dustrial and mine atmospheres and produce the harmful effects. A respirator which would not effectively remove dust below 2 microns could be 98% efficient provided the test was made against concentra tions that contain Only a small amount of particles below 2 microns in size. IX SC 030737 62. Q . H ow is (he reliability of cm efficiency T alu s a s a m ea su re of dust protection affected b y the concentration of dust in the air? A. A respirator may have high percentage efficiency and sail leak enough dust through the filter to cause harm. For example, a respirator that is 97% efficient against a concentration of 500 million particles of dust per cubic foot of air (a not unusual case) would leak I f million particles which, is more chan is considered a permissible amount of dust with a high silica concent m the air breathed T he Bureau o f Mines approval is given only to respirators that do not leak enough dust to bnng the dust tn the air breathed above permissible limits. S3. Q . W h a t is m e a n t b y com fort a n d c onvenience? A . The following factors are elements o f comfort and convenience: 1-- Resistance to breathing. 2-- Degree of impediment and encumbrance to vision and normal performance of work. 64. Q . Should com fort a n d protection b e considered se p a ra te ly ? A. N o Any acceptable respirator must give both adequate protection and an acceptable degree of comfort. 65. Q. W hat is m eant by cost oi m aintenance? A . T he cost of maintenance is the expense involved in keeping the respira tor in an efficient, comfortable, and clean working condition. Low cost of replacement of filters is an important element in this expense. 66. Q . W h at is m ea n t b y e a s e of m aintenance? A. By ease of maintenance is meant the ease w ith which a dust laden respirator can be restored to its initial high degree of efficiency and comfort through: 1-- S ervicing. 2-- Replacement of filters. 3-- Sterilization. 67. Q . How can respirators b e sterilized? A . M.S_A. Cleaner-Sanitizer powder when mixed with warm w ater malms an effective cleaner and sanitizer for respirators. Just mix one package (one ounce) to a gallon of warm (about 120" F ) w ater and immerse soiled respirator in this solution. Scrub gently with soft brush until respirator is clean. Rmse in plain warm water and air dry. i> SC 030738 Mechanical Filter Respirators For Protection from Dusts, Mists and Fumes Manufactured by Mine Safety Appliances Company M-S-A "CO M FO '' DUST RESPIRATOR W ith Type F Filters ! M-S-A DUSTFOB RESPIRATOR ! ; M-S-A "COM FO" RESPIRATOR W ith Type S Filters is SC 030739 Air Line Respirator Equipment Manufactured by Mine Safety Appliances Company M.S.A. AIR LINE RESPIRATOR W ith "Comfo" Cushion Facepiece M.S.A. ABRASIVE MASK SC 030740 Accessory Equipment for Air Line Respirators Manufactured by Mine Safety Appliances Company M.S.A. PORTABLE AIR FILTER AND REGULATOR Entirely self-contained and readily portable, this unit removes oil mists, oil vapors, water, and ptpe scale from compressed air. and provide* effective protection against excessive and variable pressures in the air supply. It ts designed lor attachment to the mam compressed air lines and has a capacity of one to ax take-off lines to supplied air maJcs and respirators. The M S A . Portable Ait Filter and Regulator u equipped with a chemical fill for efficient removal of odors and vapors, and a mechanical separator which removes Oil, water and d m from incoming compressed air. A built-in pressure regulator governs air pressure at a predetermined safe lim it i M.S.A. CLEANAIR BLOWER M S A . Q eaoA ir Blowers wash, cool, and humidify the air they supply--by utilizing a small, constant flow of water through the rotor chamber. The water also acts as a com pression seal, eliminating alt metal-to-raetal contact. Since no lubrication ts necessary for the operation of Q eenA ir Blowers, no oil or grease comes in contact with delivered air. No auxiliary air filter oc regulator vs neces sary with a C&anAir Blower. M S.A. ClcanAir Blowers are furnished in a u/tde range of sues to meet desired respi ratory requirements. 15 SC 030741 Air Sampling Equipment for Dusts, Mists and Fumes M anufactured b j Mine Safety Appliances Company M.S.A. MIDGET IMPINGER The M 5-A . M idget Imptnger samples at a rate of one-tench ot a cubic toot per minute ind is operated by a hand-cranked, positive* acting 4 cylinder pump of ingenious design Tins pump, m conjunction with a vacuum regulator, maintains an unfluctuating action regardless of minor variations in the rate or iraooehne&s ol cranking. The apparatus coatatned m a compact, sturdy carrying case complete with nine calibrated glass antpltni* tube. The light weight, null dimension, and alraOkt effortless operation of this modem instrument greatly broaden the held id dust urnplicg by the uoptnger method. Isolated locations, confined spaces, lack of electric cur* rent or compressed air presents no barriers to the M.S.A. M idget tmpinger. VL5.A. ELECTROSTATIC Dust and Fume Sampler Bvd>kt No This instrument, designed for quantitative sampling of dust, fume, and mist, employs the principle of preiom satioa with electrostatic preapitation. T he u n it is compact and easy to use for sampling from the general ionos phere or from stacks or ducts; it u the only e fia e n t sampler for fumes, parocularfy lead fumes. Other feature* are Urge sampling volume ot 2 cu. ft. per minute penmtimg accurate determinations of very low concentrations of atmospheric particulate matter: flow measure ment w ith orifice and mechanical manometer -no liquids to spdl; extension tube for sampling ac breathing level with apparatus on the floor: and collection of samples in a ipemal aluminum tube permitting determine' none by weighr, count or chemical analysis. This precipitator operates on 110*120 volts, 60 cycle, alternating current. Case men tions are 16 x x 10V4 inches, famed mi V . S. A. $6* SC 030742 PERTINENT QUESTIONS and ANSWERS CONCERNING DUSTS MINE SAFETY APPLIANCES Braddock, Thomas and Meade Streets PITTSBURGH, PA. CO. Foreword 1A H ERE is an increasingly wide and intense interest in harmful effects of breathing dusts, especially those that contain free silica and cause the disease of the lungs known as silicosis. Interest has been further stimulated by the work of Federal agencies and States in industrial hygine, and by legislation that provides compensation for injury to health. As a result many persons in industry who are responsible for healthy working conditions have been rather suddenly confronted with the need of becoming ac quainted with dust diseases, nature of dust, its composition, size of parades, and the amount that is harmful, and the means for preventing exposure and protecting workmen. Much has been said and published on these subjects, but it has been presented in terminology and language of a specialized, technical, and scientific nature that is either meaningless Co most persons or creates a good deal of misunderstanding. Also, considerable confusion has arisen from the conflicting opinions and views that have been widely expressed. In this booklet it is endeavored to present some of the questions that anse continually regarding the nature and effects of dusts, and to answer these questions in simple and insofar as possible non-techmcal language. J. T. RYAN, Mme Safety Appliances Co. Pertinent Questions and Answers Concerning Dusts 1. Q. W hat are the usual dasaificatians oi air-carried particles? A. A ir-earned parades are usually classified into three groups: 1-- Dusts 2-- Fumes 3-- Mists 2. Q. W hat are dusts? A. Dusts are mechanically generated p arad es resulting from such opera tions as drilling, blasting, crushing, and handling of rocks and minerals: sand-blasting', stone and granite cutting; grinding and polishing; and all similar operations and processes. The p arade sites of air-carned dusts are usually below one micron with an average sire of 0 5-0.7 microns. 3. Q. W hat is a micron? A. A micron is a unit of measurement, one micron being equal to about 1/25.000 of an inch or in other words it would require 25,000 parades each one micron in sire laid end to end to measure one inch. 4. Q. W hat is the sm allest partide that can be seen by the naked eye? A. The smallest parad e visihle to i person w ith average eyesight is about 100 microns in dimension. This is 1/250 of an inch. 5. Q. How does this com pare w ith the size oi die average partide found id air-bom industrial dusis? 4 A. This is one hundred and fifty to two hundred times the sire of tho| average partide found in industrial atmospheres. In other words, the parades of dust of significance from the standpoint of health are only a small fraction of the sire that is visible to the naked eye. 6. Q. W hat range oi partide sires is important? A. T he particles below 5 microns are o f most importance as dusts of larger size settle out of the air very quickly and are not likely to be breathed. In general the parades of dust found in industry arc below one or two microns with as much as 50% below 0.5 or 0.7 micron. Under some conditions the sire may-be larger or smaller than this general site range. 7. Q . W hat are fam es? A. Fumes are parades produced in chemical and metallurgical processes, welding, and similar operations, or by the decomposition of chemicals by heat and combusaon. T he average partide sire is less than th a t of dusts. Most fumes have an average p a rad e size of 0.2-0.3 microns. The important harmful fumes are usually the fumes of metals or their compounds such as lead oxide, zinc oxide, and cadmium oxide. Owing to their small particle are fumes are even more difficult to remove by filters than are mechanically generated dusts. 2 SC 030745 CAtftesy ul U.5. B orn of lit** 10 15 5 1 2 MICRONS I 5 SILICIOUS DUST FROM M INE AIR Magnified 100 hms The d u n parades and dels shown m d m illustration are m atmfied 100 iim their actual size. If tltey were not magnified to tfcu extent all of the parades and does would be invisible. vn the largest or 10 micron size would be only one-tenth that which could be seen with the naked eye and the average parade would be less than one' hundredth the visible size. This illustrates that the smallest particle th a t can be seen with the nailed eye is about 100 microns m dimension and that all air carried dust is invisible. 8. Q. W hat a re mists? - A . Mists are particles of liquids or mixtures o f liquids and solids; in other words, w et parades. Their size depends upon the process b y which they were generated. Good examples of mists are: the so-called "fogs" produced in spray coating with materials such as siliceous glazes or paints that contain lead, and the chromic acid mist produced during chromium plating. 9. Q. W hal dusts are dangerous? A . The effect of many industrial dusts on health is not known as yet since the physiological reactions of most dusts do not appear for some years, and die use of many dust producing compounds is relatively new. Most authorities agree that most dusts ate dangerous in some degree if breathed in sufficient concentration over a period o f tune. T he safe course is to eliminate all dust down to the limits that are considered good engineering practice in dust control. 10. Q. How are dusts classified in relation to their effects on h e a l t h ? A. Dusts axe usually classified into three groups: 1-- Tome or poisonous dusts. 2-- Nuisance dusts. I 3-- Fibrosis-producing dusts. 3 <r I SC 030746 11. Q. W h a t is a toxic dust? A. A toxic dust is usually considered co be the dust of a poisonous ma terial, such as lead and arsenic or their compounds, that produces injury to organs such as the circulatory system, heart, liver, kidneys, brain, and nervous system. W hen a poisonous dust is inhaled and deposited in the lungs, it dissolves and is earned by the blood to all organs and tissues. It may also be deposited in the mouth and throat by inhalation or contamination w ith dirty hands, and later swallowed and enters the body through the digestive tract. 12. Q. W h at is a n u isa n c e dust? A. A nuisance dust is one that a often associated with an increase in respiratory diseases (such as, colds in the head, bronchitis, pneumonia, and tuberculosis). Many such dusts are discomforting to the worker and may be dangerous. They do not produce toxic effects or farm fibrous tissue in the lungs. 13. Q- W h a t is a fibrosis-producing dust? A. It is one that through its action in the lungs causes a disease of the normal lung tissue and a replacement of this vital tissue with fibrous (scar) tissue. 14. Q- W h a t is pneum oconiosis? A . It is a term applied to any lung disease arising from inhalation of dust. 15. Q. W h a t is silicosis? A. It is a disease of the lungs in which the normal lung tissue is replaced by fibrous (scar) tissue due to breathing air that contains free silica dust (silicon dioxide, SiO ,). 16. Q. C a n silicosis b e p ro d u c e d b y a n y s u b s ta n c e o th er th a n free silica? A. Silicosis is a specific disease caused only by breathing free silica. How 1 ever, there are indications that the presence of other kinds of dust and'" gases may influence the effect of silica m the lung 17. Q . W h a t is n o n e ts ' pfhisis? A. It is a term used frequently tu designate a condition of silicosis com plicated by the presence of tuberculosis. 18. Q . W h a t is anthraco-nilicasiB (m iner's a sth m a )? A. It is a chronic disease of the lungs in which the normal lung tissue is replaced by scar tissue caused by breathing excessive amounts of a mixture of silica dust along with coal dust. 19. Q- W h a t is ashesfosis? A. It is a disease of the lungs in which the normal lung tissue is replaced by fibrous (scar) tissue due to breathing air that contains asbestos dust. 20. Q. W hat a r e th e principal factors in determ ining the h ealth hazard from ail-carried dust? A. The following factors are usually important: 1-- Chemical composition of the dust. 2-- Am ount of dust in the air. 4 * SC 030747 3-- Size of the dust particles. A-- Length of time of exposure, 5--A n understanding and interpretation of these factors in terms of the effect of dust on persons. 21. Q. W hat is m eant by chem ical com position of a dust? A. All materials such as rocks and minerals are not w hat might be termed pure chemical compounds, but are m atures of several chemical com pounds. T he chemical composition is the kind and amounts of these var ious components. In the case of a Lea-bearing substances, the amount of silica present may vary from almost nothing to 100%. The amount of silica present is obviously the im portant factor in the silicosis pro ducing properties of a dust. 22. Q. Is the chem ical com position of the dust in the air the sam e as the substance that is being drilled, handled, crushed, or processed? A. A s mast dust producing substances dealt with in industry contam more than one mineral component, some of these components will crush or disintegrate more easily than others and thereby form a larger pro portion of small parades. These smaller particles will tend to pre dominate m the air while other constituents being larger will settle out. For this reason, the composition of the dust in the air may vary greatly from the composition of the rock or mineral. 23. Q. W hat is the im portance of the chem ical com position of a dust? A. The chemical composiuon reveals the harmful constituents and their amount, and constitutes the basis for judging the harmful qualities of the dust. This information is an important factor along with concentrauon and time of exposure in determining the hazard. 24. Q. W hat are the important steps in determ ining the chem ical com position of a dust? A. It is necessary to first obtain a sample that represents the dust m the air breathed, and then subject the sample to methods of analysis that are known to give accurate results for the constituents desired. 25. Q. How rirw a representative sam ple ol the dust in the air breathed b e obtained? A . I t can be obtained only by collecting the dust from the air. Samples o f pieces of rock or settled dust do not necessarily bear any close re lation in composition to the dust floating in the air. 26. Q. How m n a sam ple of sufficient size for chem ical an alysis be collected from the air? A. Collection from the air can be accomplished by long and continuous operation of dust collection devices such as the impinger. electrical or electrostatic precipitators or filter bag type of collectors. 27. Q. W hat m ethods are generally used for determ ination of the percent of free silica in dusts? A . I-- By observing the action of the small dust particles on light with die aid o f a special type of microscope. T his is known as the petrographic method. 2-- By chemical analysis. 3-- By observing the action o f the parades on X-Rays. 5 28. Q. What are the lim itations of the petrographic method? A. It is impassible by this method to examine individual particles below one or two microns in size and since most of the air-carried dust is below this size range, one must rely on petrographic information obtained from particle sizes that are above those of primary significance. 29. Q. What are the lim itations of the chem ical method? A. There is no known chemical method that is specific for free silica (S1O 1) when this constituent is present with silicates. However, by observing the difference in die rate at which silica dissolves in certain acids as compared with other constituents a rough estimate can be obtained for some dusts, but with others the method will be greatly in error. 30. Q . What are the lim itations of the X-Bay method? A. The X-Ray procedure can be used for making specific determinations of free sdica in a very small sample such as 25 to 50 milligrams. The disadvantage of the method is that it requires very expensive ap paratus. 3L Q. W hat is meant by size of particle; haw is H expressed? A. The size of the particle is its largest dimension, usually expressed in microns. It has been stated by authonties that if all dust below one micron m size could be eliminated, nearly all dust disease would be eliminated. 32. Q. How can the sine of dost particles be determined? A. The size o f dust particles is measured by means of a microscope or by projection of the dust particles on a screen similar in general principle to ordinary lantern slide projection. T he particles as seen m the microscope or projected are then measured. 33. Q . How quickly does fine dust settle? A. It settles very slowly. In the tabic given below will be found the time in minutes estimated for silica dust of given sizes to fall one foot in still air. Size in microns Time in minutes to fall one foot A 590. Vi 187. l 54. 2 14.4 5 2.5 34. Q. D oss nW im of visible dust m ean absence of fine dost? A. No. T he operation may produce only fine dust or the visible dust may have disappeared owing to its rapid rate of settling, leaving the invisible but harmful dust in the air. 35. Q. W hat is meaztt by dust concentration,' how is it expressed? A. The concentration is the amount of dust suspended in a given volume of air. It is usually expressed in number of particles in a cubic foot of air, or millions of particles in a cubic meter of air, or in a cubic s % SC 030749 centimeter. It may also be expressed as the weight of dust m a given volume of air as milligrams m a cubic meter o r grains m a cubic foot. 36. Q. W hat is the relation am ong these units of quantity? A. Num ber of cubic feet times .02832 gives number of cubic meters (m'). Number of cubic meters times 35.31 gives number of cubic feet. Number of cubic feet tunes 28,317 gives number of cubic centi meters (cc.) Number of milligrams times .001 gives number of grams. Num ber of grains times 64.80 gives number of milligrams. t Num ber of grains times 00229 gives ounces (avoirdupois) 37. Q. How can the concentration in particles per cubic centim eter be converted to number of particles per cubic foot? A. M ultiply the number of particles per cubic centimeter by a million and divide by 35.31 to get number of particles per cubic foot. 38. Q. How m any particles oi air-carried dust otb in one milligram w eight of dust? A. It has been found that one milligram of silica dust of the site range present in industrial atmospheres contains about 200 to 300 million particles. 39. Q. W hat apparatus and m ethods are generally used for determin ing dust concentrations? A. The impinger, konimeter, and electrical precipitator are the instru ments generally used for this purpose. Details of the instruments and methods can be found in publications of the United States Bureau of Mines and the United States Public Health Service. 40. Q. W hat is an impinger? A. I t is a device by which air is drawn a t a definite rate of flow and at high velocity through a small nozzle so directed as to strike a glass plate immersed in liquid such as water, alcohol, or a mixture of these liquids. T his high velocity action causes the dust particles to be "w etted" and retained in the liquid. Some of this liquid is then examined under a microscope and a count of the dust particles present is made. It is a rather bulky instrument, requires training in use, care in handling, but has acceptable accuracy. I t is the instrument most commonly used at present in the United States for dust determinations. It can be used for determining the number of dust particles of any kind of dust not soluble in the liquid in which it is collected. It can be used for soluble dusts by evaporating the solution, thus leaving the dust as residue. The soluble dust may also be determined by chemical means. A s the impinger apparatus collects the dust from a rather large volume of air taken continuously over a considerable period of tune, the results are more representative of average conditions than those obtained by the use of an instrument that collects instantaneous or grab samples. 41. Q. Whcrt is a konimeter? A. It is a device by which a small sample of air, usually 5 cc., is drawn through a small nozzle and directed in the form of a jet onto a glass plate coated w ith vaseline or microscope jelly. By this means dust 7 m SC 030750 particles are deposited on the plate. W ith one design of kommeter the number of particles of dust are counted with a microscope directly attached to the instrument; with another type these samples are taken to the laboratory for counting w ith an ordinary microscope. The kommeter takes an instantaneous or grab sample rather than a con tinuous sample as taken by the impinger or electrical precipitator. It is a rapid method and requires very little sampling skill. For obtaining average dust concentrations over a period of time it is necessary to make a senes of kommeter determinations and average the results. 42. Q. W hat is a n electrical precipitator? A. It's a device by which air is drawn at a definite rate of Sow through a high voltage electrical field so arranged as to cause any dust to be re moved and deposited on a foil or paper. The dust collected can be determined either by counting the number of particles with a micro scope or by weighing. It is an efficient method but requires a source of electrical energy. A s with the impinger, the electrical precipitator collects the dust continuously from a comparatively large volume of air and thus provides a sample that represents average conditions. It may even be used to collect a sample that is large enough for chemical analysis. 43. Q. How can exposure be determined? A. Since exposure is a term that involves concentration, particle site, chemical compoaticn, and duration of time, it is necessary to determine all of these in order to properly evaluate the degree and extent of exposure. The time element requires an accurate job analysis m which is recorded die amount of time spent by a workman at his various operations. This record should then be associated with die dust con centration, particle size, and chemical composinon of the dust a t each operation and the average over all daily exposure determined. For Example-. Summary of Dust Exposure of ley n er Drillers in a Granite Quarry Activity Average exposure in millions of parades per cubic foot. Hours spent in each activity Parride hrs. (millions per cubic foot) Drilling._______ ___ _... 213.4 4 Changing drills....... ... 9.8 i W atching drills...... ... 8.0 2 Broaching----- ------ ... 6.0 n Blowing off holes..... 1085 0 A 853.6 9.8 160 4 .> 271.3 T otal. ...................... 8 1155 2 1155.2 particle hours in millions per cubic foot 144.4 million particles per g [y. TMcubic foot. Average expos ' ure throughout the day. Table from U. S. Public Health Bulletin 217 by Bloomfield and Dallavalle. 8 % SC 030751 * I 44. Q . What is a respirator? A, A ny persona] protective device designed to prevent the wearer from inhaling the harmful constituents in bis surrounding atmosphere is called a respirator. 45. Q. What is a supplied-air or air-line respirator? A. It is essentially a hose line through which air that is safe to breathe is t conveyed to a facepiece worn by the workman. The air may be sup plied from the compressed air line although preferably it should come from a separate blower unit designed to furnish air free from distasteful or harmful impurities. 46. Q. What harmful or objectionable constituents might b e present in high pressure air as produced by an ordinary reciprocating type of compressor? A. A ir from this source may contain Oil odors, mists of cal or water, particles of rust or dirt from the air receiver or air lines, and in case of improper compressor operaaon there may be burning of the lubri cants with the formation of carbon monoxide. 47. Q . What precautions should he taken to lessen the danger from air contam ination in the use of reciprocating type of air compres sors? A. Good maintenance and care in operation of the compressor, tempera ture indicators on the outlet side of compressor, and carbon monoxide detecting equipment or carbon monoxide alarms on the outlet side to give indication of the presence of any carbon monoxide. Individual compressor units so constructed as to make generation of harmful gases i impossible are desirable sources of clean air for air line respirators. The M.S.A. Clean A ir Blower is designed to fill this need. .4 8 . Q. W hat is a chem ical filter respirator? A. i t is a respirator designed for removing gaseous constituents from the air breathed. The filtering materials m these respirators are usually granules chat react with the harmful constituents and remove them. 49. Q. What is a m echanical filter respirator? A. A mechanical filter respirator is a device that removes by mechanical filtration the particles of harmful constituents from a ir that passes through it. These devices include dust, mist, and fume respirators. Bach of these types of mechanical filter respirators is designed to protect the wearer against the particular kind of matter to be dealt with. ! 50. Q. What is a United States Bureau of M ines "approved" mechani cal filter respirator? A . It is a respirator that has officially passed the rigid test requirements of the United States Bureau of Mines as outlined in that Bureau's A p proval Schedule No. 21. 51. Q . W h at is U nited S ta te s B u re au of M ines sc h e d u le N o. 21? A. It is a publication that describes the requirements and tests that a respirator must meet in order to obtain the approval of the Bureau of 9 SC 030752 Mines. Free copies of this publication may be obtained upon request from the United States Bureau of Mines, W ashington, D. C. 52. Q For w iud types oi m echanical filter respirators does the Bureau of M ines schedule No. 21 provide approval requirem ents? A. Schedule No 21 provides approval requirements for mechanical filter respirators for protection against mechanically generated dusts {known as Type A respirator): fumes of various metals {Type B ). and mists such as chose from chromic acid and from spray coating in the absence of harmful vapors ami gases (Type C ) Combinations of these types may also be approved. 53. Q. Who m akes the approved tests? A. The Bureau of Mines makes the tests at its Pittsburgh Experiment Station where experienced personnel and complete laboratory facilities i for dust investigations are available ! 54. Q . W hat are die general perform ance requirem ents that a m echan ical filter dust respirator m ust give in order to obtain the ap ' prervai of the Bureau of M ines? A. The general features of the performance requirements are: . 1-- Dust-tight fit of the facepiece. 2-- Reduction of dust in the inhaled air below an amount that causes harm. 5-- A resistance to breathing that is below that which produces discomfort. i-- A satisfactory' degree o f convenience, durability, and service. Coal Miner locating COMJFO RESPIRATOR 10 SC 030753 55. Q. W hat is the size oi the dust particles used by the United States Bureau oi Mines in the approval tests oi respirators? A. The dust particles used m the tests are 9 i% below 1 7S microns and 50% below 0 6 micron These site characteristics are very similar to chose found in the aemospheres of mines and industrial plants 56. Q. W hat severe dust filtering and resistance performance must a m echanical filler dust respirator give to pass the approval test? A ir th at contains fifty milligrams per cubic meter (approximately 300 t * to 500 million particles per cubtc foot) of dust of the small sice specified by the Bureau of Mines is drawn through the respirator at a rate of ?2 liters a minute, or at approximately the rate at which air is breathed by an average man doing work The coral amount of dust that leaks through the respirator in a 90 minute test penod during which 2.88 cubic meters or 100 cubic feet of air arc passed must not exceed 3 0 millierams or 0 0001 ounces The resistance to inhalation when tested with air flowing through the respirator at S' liters a minute must at no time exceed 2 inches of water column. This resis tance is below that which causes discomfort. 57. Q. Axe the Bureau ai M ines approval requirem ents unnecessarily exacting and impractical? A. No. The approval requirements in schedule No. 21 represent the mini mum protection that a respirator should give in order to protect the wearer adequately. f 11 0 SC 030754 58. Q. W hat az9 the most important features of a respirator? A. 1--Adequate respiratory protection. 2--Comfort and convenience. 3--Ease and cost of maintenance. 59. Q. What is the Comfo Respirator? A. It is a particular type of respirator manufactured by the Mine Safety Appbaoces Company that is approved by the U S Bureau of Mines it was the 6rst respirator to pass this Bureau's approval tests. It has filters of specially treated cellulose for removing the dusts of very small sice that are present in industrial atmospheres. The filters are pro tected from damage or contamination by a metal covering and arc attached to both sides o f an ail rubber facepiece. It has a large filtering area and low resistance to breaching. SO. Q. How does the Comfo Respirator m eet the requirem ents for adequate respiratory protection? A. The protection afforded by the Comfo Respirator is certified by the United States Bureau of Mines approval which it carries as i result of having successfully passed the approval tests against dusts of <i particle sire 95 % of which are less than 1 7S microns anil ' 0 f~c less than 0 60 microns. T his is the range of particle sires usun lly found for mine and industrial dusts. 61. Q . W hat is m eant by the efficiency of a respirator: and w hat test facts concerning efficiency must be known to determ ine if a respirator gives adequate protection? A. The efficiency of a respirator is the percentage of the dust in the air that is retained on the filter. A t least three very important facts should be known in order to determine if a respirator, that has a reported high efficiency, also gives adequate protection: 1-- The dust concentration used in determining the efficiency figure 2-- T hat the p arade sue of the dust used in determining the efficien cy represents the sue of the dusts found in industrial atmospheres 3-- T hat the percentage inefficiency, or the amount of dust that leaks through, does not exceed that which is safe to breathe. 82. Q. How does variation in particle size effect the reliability of an efficiency value of a respirator? A. The statement that a respirator is efficient means little if the p a rad e size range of the dust tested ts not given because the difficulty in removing dust increases as the p a rad e sue decreases so that dusts below i to 2 microns are much more difficult to remove than the larger sizes, yet it is parades below 1 to 2 microns that predominate in in dustrial and mine atmospheres and produce the harmful effects. A respirator which would not effectively remove dust below 2 microns could be 98$i efficient provided the test was made against concentra tions that contain only a small amount of particles below 2 microns m size. 12 SC 030755 S3. Q. How is the reliability of an efficiency value a s a m easure of dust protection affected by the concentration of dust in the air? A. A respirator may haw high percentage efficiency and still leak enough dust through the iter to cause harm. For example, a respirator that is 91c/c efficient against a concentration of ' 00 million particles a t dust per cubic foot of air (a not unusual case) would leak 15 million particles which 13 more than is considered a permissible am ount of dust with a high silica content in the air breathed. The Bureau of Mines approval is given only to respirators that do not leak enough dust to bring the dust m the .ur breathed above permissible limits. 64. Q, W hat is meant by comfort and convenience? A. The following factors arc elements of comfort and convenience 1--Rea stance to breathing. Z--Degree of impediment and encumbrance to vision and normal performance of work. S3. Q. Should comfort and protection be considered separately? A. No Any acceptable respirator must give both adequate protection and an acceptable degree of comfort. 66. Q. How does the Corafo Respirator m eet the comfort requirem ent? A. The comfort of the Comfo Respirator is assured by its low breathing resistance, light weight, and lack of encumbrance to the wearer's vision and movement M S A Comfo Respnotor 100m by worker m ceramic plant 15 SC 030756 67. Q. W hat is meant by cost of m aintenance? A. The cost of maintenance is the expense involved m keeping the respira tor in an efficient, comfortable, and clean working condition. Low cost of replacement of filters is an important element in chis expense. 68. Q. How d oes the Cem io Respirator meet the low m aintenance cost requirem ents? A. The low maintenance cost of the Comfo Respirator is given by the low cost of the replaceable filters and the short tunc required for ^g*. replacement. 69. Q. W hat is meant by ease of maintenance? A. By ease of maintenance is meant the case with which a dust laden respirator can be restored to its initial high decree of efficiency and comfort through. 1-- Servicing. 2-- Replacement of filters 3-- Sterilisation. 70. Q. How d oes the Comfo Respirator meet this requirem ent far ease of m aintenance? A. The low cost of Comfo Respirator filters permits discarding of the dust laden fiber and replacement with new filters. This avoids the cleaning of filters and provides a new and clean filter with the initial high degree of protection and comfort. 71. Q. How can respirators he sterilised? A. Scrub rubber and metal parts with soap and water. Rinse m warm w ater and immerse for 10 minutes in a solution of formalin made by placing one part of 40% formaldehyde solution into 9 parts of water. Instead of the formalin solution, 1 part of carbolic acid in. 33 parts of water, or 1 part of Lysol m 50 parts of water, or 8 parts of denatured alcohol in 3 parts of water may be used. All respirators should be thoroughly rinsed with w ater immediately after immersion in the sterilizing solution and put in a clean place to dry. 72. Q. How d oes the Comfo R&pircifor permit ea sy and thorough steril ization and cleaning of a ll parts? A. Owing to the low cost of filters, these parts can be discarded and the entire remaining part of the respirator thoroughly washed and steri lized. A fter replacement of new filters the respirator is in its original clean and efficient condition. This permits daily sterilization of all parts and avoids the growth of bacteria and danger of contamination from parts that cannot be completely srenlized. 73. Q. How d oes the Comfo Respirator meet the requirem ents of indus tries for respiratory protection? A. The Comfo Respirator is certified by the United States Bureau of Mines Approval as giving adequate respiratory protection; it is com fortable and convenient; it is easily maintained and the cost of filter replacement is low. 14 SC 030757 Equipment for Protection from Dusts M anufactured by Mine Safety Appliances Company M.S.A. COMFO RESPIRATOR The M .S A Comlu Du*e and Mtot Rcsptracor is a mechanical biter type respirator chat was developed to protect workmen from breaching dust >uch as sihea. coal. iron, asbestos, and other cirmiar air carried par ticles of the very small sices lound in indus trial atmosphere* it Kill also protect against the harm Iul liquid mist produced in chromium plating and the m w of vitreous enamels. This respirator baa been otScmDy approved by the U. S Bureau of Mi n o , .Approval N'o 2101 The M S A . Com to Lead Dust Respirator is identical in design with the D ust and Mist Respirator except rhe cellulose Iters arc specially treated for filtering out lead dusts ot '-mall particle sixes. It is officially approved by the U 5 Bureau of M m c\ Approval N'u 2107 M.S.A. AIR LINE RESPIRATOR The M.S.A. .Air Line Respirator provides protection Irom gases, vapor, duts, and fumes by providing the wearer with an ade quate supply a i air lor breathing require merits. Both rhe M S A . A ir Line Respirator and the M S.A . Abrasive Mask (shown later) have free-wheeling control valves to insure against accidental bumping and chang ing of air flow, and a quick release connection 10 case the air supply fails or becomes un usable for any reason. t* SC 030758 M.S.A. ABRASIVE MASK T he M S .A , Abrasive Mask is a light, comfortable. fresh air supplied unit designed for respiratory proteccin Irum the high concentrations of fine dust produced by abra>nc blasting with sand or shot, and for protection of the head and -houiders from impact and abrasion by the high velocity rebounding particles It gives protection from d u sts fumes, gases, and vapors. M.S.A. CLEAN AIR BLOWER The M 5 A. Clean A ir Blower is specially designed for supplying air that 19 cool. dean, humidified, and free from obnoxious or harmful gases to air line respirators, sand blast hoods, and helmets. It is a rotary type in which water is u*ed as a compressor seal, cooling medium, humidifier, air washer, and dust remover There is no internal lubrication and no contact o f the air with oil, grease, or contaminating agents. 16 PfitMTCD tM V, 9. A. % SC 030759 ' f ^ 0 O *' ' " ' * * f f ' ;- f -7 --'* 7 ^ 1 ^ = f | SC 030760 Foreword 1jL H ERE is an increasingly wide and intense interest in harmful effects of breathing dusts, especially those that contain free silica and cause the disease o f the lungs known as silicosis. Interest has been further stimulated by the w ork of Federal agencies and States in industrial hygiene, and by legislation that provides compensation for injury to health. A s a result many persons in industry who are responsible for healthy working conditions have bean rather suddenly confronted w ith the need of becoming ac quainted with dust diseases, nature of dust, its composition, site of particles, and the amount that is harmful, and the means for preventing exposure and procecnng workmen. M uch has been said and published on these subjects, but it has been presented in terminology and language of a specialized, technical, and scientific nature that is either meaningless Co most persons o r creates a good deal of misunderstanding. Also, considerable confusion has arisen from the conflicting opinions and views that have been widely expressed. In this booklet it is endeavored to present same o f the questions that arise continually regarding the nature and effects o f dusts, and to answer these questions in simple and insofar as possible non-technical language. J. T . R Y A N , M m Safety Appliances Co. Pertinent Questions and Answers Concerning Dusts 1. Q . W h a t a re the usual classifications o i air-carried particles? A . Air-carried particles are usually classified into three groups: l-- Dusts 1-- Fumes J--Mists 2. Q. W h at are dusts? A. Dusts are mechanically generated particles resulting from such opera tions as drilling, blasting, crushing, and handling o f rocks and minerals: sand-blasting; stone and granite cutting; grinding and polishing; and all similar operations ant) processes. T he particle sites of air-cam ed dusts are usually below one micron w ith an average sire of 0.5-0.7 microns. 3. Q . W hat is a micron? A. A micron is a unit of measurement, one micron being equal to about 1/25,000 o f an inch or in other words it would require 25,000 particles each one micron in sice laid end to end to measure one inch. 4. Q . W hat is th e sm allest particle th a t camb e se e n b y th e n ak ed eye? A . T h e smallest particle visible to a person w ithaverage eyesight is about 100 microns in dimension. This is 1/2 5 0 o f an inch. 5. Q. How does this com pare w ith the size , of the average particle found in air-bom industrial dusts? A. This is one hundred and fifty to two hundred times the sire of the average particle found in industrial atmospheres. In other words, the particles of dust of significance from the standpoint of health arc only a small fraction of the sirs that is visible to the naked eye. 6. Q. W hat ran g e of particle sizes is im portant? A . T he particles below 5 microns are of most importance as dusts o f larger sire settle out of the air very quickly and arc not bkely to be breathed. In general the particles of dust found in industry are below one or two microns w ith as much as JOfo below 0.5 o r 0 7 micron. U nder some conditions the sire may be larger or smaller than this general sire range. 7. Q. W hat a re fumes? A . Fumes are particles produced in chemical and metallurgical processes, welding, and similar operations, o r by the decomposition of chemicals b y h eat and combustion. T he average particle sire is less than th at of dusts. Most fumes have an average particle sire o f 0.2-0.3 microns. T he important harmful fumes are usually the fumes of metals or their compounds such as lead oxide, rinc oxide, and cadmium oxide. Owing to their small particle sire, fumes are even more difficult to remove by filters than are mechanically generated dusts. 2 \ SC 030762 .IC J--V\akMiUvk C caryetr o f O .S. b m e 4 M o w ID IS 5 3 2 MICRONS I .5 SILICIOUS DUST FROM MINE AIR Magnified 1O0 time* T h e dust pomelo* and dots shown m this illustration art magnified 100 a m ts thetr actual sac. 1/ they were not magnified to thi* extent all o f the particle* and dots would be iiu-uibie. Even the largest or 10 micron nee would be only one-tenth dust which could be seen with the n a \ed eye and the average particle would be lest than one* hundredth the visible stze. T in s illustrates that the smallest particle the: can be seen with the na^ed eye t* about 100 micron* in dm entton and that all air ta m e d dust i* inritfble. 8. Q. W hat are mists? A . Mists are particles of liquids o r mixtures o f liquids and solids; in other words, wet particles. Their she depends upon the process by which they were generated. Good examples of mists are: the so-called " fogs" produced in spray coating wirh materials such as siliceous glares o r paints that contain lead, and the chromic arid mist produced during chromium plating. 9. Q. W hat dusts a re dangerous? A . T he effect o f many industrial dusts on health is not triow n as yet since the physiological reactions of most dusts do not appear for some years, and the use o f m any dust producing compounds is relatively new. M ost authorities agree that most dusts are dangerous in. some degree if breathed in sufficient concentration over a period of time. The safe course is to eliminate all dust down to the limits th at are considered good engineering practice in dust control ' 10. Q . H ow a re d o s b classified in relation to their effects on health? A. Dusts are usually classified into three groups: 1-- Toxic o r poisonous dusts. . . 2--Nuisance dusts. ' 3-- Fibrosis-producing dusts. 1 \ 11. Q . W hat is a toxic dust? A . A toxic dust is usually considered to be che dust of n poisonous ma terial, such as lead and arsenic o r their compounds, that produces injury to organs such as the circulatory system, heart, liver, kidneys, brain, and nervous system. W hen a poisonous Ju st is inhaled and deposited in the lungs, it dissolves and is carried by the blood to all organs and tissues. It may also be deposited in die mouth and throat by inhalation or contamination with dirty hands, and later swallowed and enters the body through the digestive tract. 12. Q . W hat is a nuisance dust? A . A nuisance dust is one that is often associated w ith an increase in respiratory diseases (such as, colds in the head, bronchitis, pneumonia, and tuberculosis). Many such dusts are discomforting to the worker and may be dangerous. T hey do not produce toxic effects or form fibrous tissue in the lungs. 13. Q. W hat is a fibrosis-producing dust? A . I t is one that through its action in the lungs causes a disease of che norm al lung tissue and a replacement of this vital tissue w ith fibrous (scar) tissue. 14. Q. W hat is pneum oconiosis? A . I t is a term applied do any lung disease arising from inhalation of dust. 15. Q . W h a t is silicosis? A . I t is a disease of che lungs in which the normal lung tissue is replaced by fibrous (scar) tissue due to breathing a ir that contains free silica dust (silicon dioxide, 5iO-). 16. Q . C an silicosis b e produced by any substance other than free s ilic a ? A . Silicosis ts a specific disease caused only by breathing free silica. How ever, there are indications that the presence of other lands of dust and gases may influence the effect of silica in th e lung. 17. Q . W hcrt is m iners* pthisis? A . I t is a term used frequently to designate a condition of silicosis com plicated by the presence of tuberculosis. 18. Q . W hat is anthraco-silicosia (m iner's asthm a)? A . I t is a chronic disease of the lungs in which the normal lung tissue is 4 t replaced by scar tissue caused by breathing excessive amounts o f a a m ixture of silica dust along with coal dust. IS. Q . W hat Is asbestosis? 1 A_ Ir is a. disease o f the lungs in which the normal lung tissue is replaced by fibrous (scar) tissue due to breathing air that contains asbestos dust. 20. Q . W hat are the principal {actors in determ ining the health hazard 3 ) {root air-aarried dust? 3 A . The following factors are usually important: i 1-- Chemical composition of die dust. J * "I 2--Am ount of dust in the air. 4 i SC 030764 3-- Sice of the dust particles. 4-- Length of time of exposure. f--A n understanding and interpretation of these factors in terms of the effect of dust on persons. 21. Q. W h a t is m e a n t b y ch em ical co m p o sitio n of a dust? A . A ll materials such as rocks and minerals are not u-hat might be termed pure chemical compounds, but are mixtures of several chemical com pounds. The chemical composition is the kind and amounts of these var ious components. Li the case of silica-bearing substances, the amount of silica present may vary from almost nothing to lOOfe. The amount of silica present is obviously the im portant factor in the silicosis pro ducing properties of a dust. 22. Q . Is the chem ical composition of the dust in the ait the sam e a s the su b sta n c e th at is b ein g drilled, h an d led , crushed, o r processed? A . As most dust producing substances dealt with in industry contain more than one mineral component, some o f these components will crush or disintegrate more easily than others and thereby form a larger pro portion of small parades. T hese smaller parades will tend to pre dominate in the air while other constituents being larger will settle out. For this reason, the composition of the dust in the air may vary greatly from the composiaon or the rock o r mineral. 23. Q . W hat is the importones of tho chem ical composition of a dust? A . The chemical composition reveals the harmful constituents and their amount, and constitutes the basis for judging the harmful qualities of the dust. This information is an im portant factor along with con centration and time of exposure in determining the hazard. 24. Q. W hat a re the im portant steps in determ ining the chem ical com position of a dust? A . it is necessary to first obtain a sample that represents the dust in che air breathed, and then subject the sample to methods of analysts th at are known to give accurate results for the constituents desired. 25. Q . H ow c a n a representative sa m p le of the dust in the a ir b re a th e d be obtained? A . It can be obtained only by collecting the dust from the air. Samples o f pieces of rock o r settled dust d o not necessarily bear any close re lation in composition to the dust floating in the air. 26. Q . H ow can a sam ple of sufficient size for chem ical analysis h e collected from the air? A . Collection from the air can be accomplished by king and continuous operation of din t collection devices such as che impinger, electrical o r electrostatic precipitators or filter bag type of collectors. 27. Q . W hat m ethods a re generally u sed for determ ination of the p ercen t of iree silica in dusts? . A . 1-- By observing the action o f the small dust particles on light w ith the aid of a special type of microscope. This a known as the petrographic method. 2-- By chemical analysis. 3-- By observing the action o f the particles on X-Rays. 1 SC 030765 28. Q . W hat a re the lim itations oi the petrographic m ethod? A. I t is impossible bjr this method to examine individual particles below one or tw o microns in sice and since most o f the air-carried d u st is below this sice range, one must rely on petrographic information obtained from particle sizes that are above those of prim ary significance. 29. Q . W h a t a re th e lim itations ol th e chem ical m ethod? A . There is no known chemical method that is specific for free silica (SiO .) w hen this constituent is present w ith silicates. However, by observing the difference in the race a t which silica dissolves in certain adds as compared with other constituents a rough estimate can be obtained for some dusts, but with others the method will be greatly in error. 30. Q. W hat are the lim itations of the X-Ray m ethod? A. T he X-Ray procedure can be used for making specific determinations o f free silica in a very small sample such as 2 5 to 50 milligrams. T he disadvantage of the method is that it requires very expensive ap paratus. 31. Q . W h at is m ean t b y size of particle; h o w is it expressed? A . T h e size of the particle is its largest dimension, usually expressed in microns. I t Has been stated by authorities that if all dust below one micron in size could be eliminated, nearly all dust disease would be eliminated. 32. Q. How can the size of dust particles be determ ined? A. The site of dust particles is measured by means of a microscope or by projection o f the dust particles on a screen similar in general principle to ordinary Lantern slide projection. T h e particles as seen in the microscope or projected are then measured. 33. Q . H ow quickly does fine du st settle? A. I t settles very slowly. In the table given below will be found the time in minutes estimated for silica dust of given sizes to fall one foot in still air. Size in microns Time in minutes to fall one foot 590. 187. 54. 14.4 2.5 34. Q . Does ab sen ce of visible dust m ean absence of fine dust? A. Ko. T he operation may produce only fine dust or the visible dust m ay have disappeared owing to its rapid rate of settling, leaving the invisible b u t harm ful dust in the air. 35. Q . W hat is m eant by dust concentration; how is it expressed? A. T h e concentration is the amount of dust suspended in a given volume of air. It is usually expressed in number of particles in a cubic foot of air, or millions of particles in a cubic meter of air, or in a cubic 6 SC 030766 centimeter. It may also be expressed a> the weight o f dust in a given volume of air as milligrams in a cubic meter or grains in a cubic foot. 3E. Q. W hat is the relation am ong these units of quantity? A. Num ber o f cubic feet times .02S32 gives number o f cubic meters (m*). Num ber of cubic meters times 31.31 gives number of cubic feet. Number o f cubic feet tunes 23,317 gives num ber of cubic centi meters (cc.) Number o f milligrams times .001 gives number of grams. Num ber of grains times 64.SO gives number of milligrams. Num ber of grains times .00229 gives ounces (avoirdupois). 37. Q. How can tho concentration in particies per cubic centimeter b e converted to number of particles per cubic foot? A. Multiply the number o f particles per cubic centimeter by a million and divide by 3f .31 to gee number of particles per cubic foot 38. Q. How m any particles of air-carried dust are in one milligram w eight of dust? A . It has been found that one milligram of silica dust of the sire range present in industrial atmospheres contains about 200 to 300 million particles. 39. Q. W hat apparatus and m ethods are generally used (or determin in g dust concentrations? A. The impinger, konimeter, and electrical precipitator are the instru ments generally used for this purpose. Details of the instruments and methods can be found in publications of the United Stares Bureau of Mines and the United States Public Health Service. 40. Q. W hat is a n impinger? A . I t is a device by which air is draw n at a definite rate of flow and a t high velocity through a small n o a le so directed as to strike a glass plate immersed in liquid such as water, alcohol, or a mixture of these liquids. T his high velocity action causes the dust particles to be "w etted" and retained in the liquid. Some of this liquid is then examined under a microscope and a count o f the dust particles present is made. I t is a rather bulky instrument, requires training in use, care in handling, but has acceptable accuracy. I t is the instrument most commonly used at present in the United States for dust determinations. I t can be used for determining the number of dust particles o f any kind of dust not soluble in the b'quid in which it is collected. I t can be used for soluble dusts by evaporating the solution, thus leaving the dust as residue. The soluble dust may also be determined by chemical means. A s the impinger apparatus collects the dust from a rather large volume of air taken continuously over a considerable period o f time, the results are more representative o f average conditions than those obtained by the use of an instrument that collects instantaneous or grab samples. . 41. Q . W hat is a konitneler? .. . . A . I t is a device by which a small sample of air, usually S c c, is drawn through a small norxle and directed in the form of a jet onto a glass plate coated with vaseline or microscope jelly. By this means dust 7 SC 030767 i 1 p arad e; arc deposited 1 the place. W ith one design of konimeter the number of panicles of dust are counted with a microscope directly attached to the instrument; with another type these samples are taken to the laboratory for counting with an ordinary microscope. T he konimeter takes an instantaneous or grab sample rather than a con tinuous cample as taken by the impinger or electrical precipitator. It is a rapid method and requires very little sampling skill. For obtaining average dust concentrations over a period of tim e it is necessary to make a series o f konimeter determinations and average the resoles. 42. Q- W hat is an electrical precipitator? A . It's a device by which air is drawn at a definite rate of flow through a high voltage electrical field so arranged as to cause any dust to be re moved and deposited on a fotl or paper. The dust collected can be determined either by counting the number of particles with a micro scope o r by weighing. It is an efficient method b u t requires a source of electrical energy. As with the impinger, the electrical precipitator collects the dust continuously from a comparatively large volume of air and thus provides a sample that represents average conditions. It mayeven be used to collect a sample that is large enough fa r chemical analysis. 43. Q . How can exposure b e determ ined? A . Since exposure is a term that involve! concentration, particle size, chemical composition, and duratiun of time, it is necessary to determine all of these in order to properly- evaluate the degree and extent of exposure. T he time dem ent requires an accurate job analysis in which is recorded the amount of time spent by a workman at his various operations. This record should then be associated w ith the dust con centracin, particle te, and chemical composition of the dust a t each operation and the average over all daily exposure determined. For Example: . Summary of Dust Exposure of Leyner Drillers in a Granite Quarry Activity Average exposure in millions o f partides per cubic foot. Hours spent in each activity Particle hrs. (millions per cubic foot) D rillin g .----------------- 213.4 4 853.6 Changing drills_____ 9.8 1 9.8 W atching drills-........ 8.0 2 16.0 Broaching___ _______ 6.0 fa 4.5 Blowing off holes...... 10S5.0 V* 271.3 T o ta l _______________ 8 1155.2 1155.2 particle hours in millions per cubic foot 144.4 million particles per g jjr --cubic foot. Average expos ' ure throughout the day. Table from U. S. Public Health Bulletin 217 by Bloomfield and Dallavalle. 8 SC 030768 1 44. Q . W hat is a respirator? A. A ny personal protective device designed to prevent the wearer From inhaling the harmful constituents in h a surrounding atmosphere is coiled a respirator. - 45. Q . W hat is a supplied-crir or air-line respirator? A . I t is essentially a hose line through which air th a t is safe to breathe is conveyed to a facepiece w orn by the workman. T he air may be sup plied from the compressed air line although preferably it should come from a separate blower unit designed to furnish air free from distasteful or harmful impurities. 46. Q . W hat harm ful or o b jec tio n a b le constituents m ight b e p re se n t in high pressure air a s produced by a n ordinary reciprocating type of compressor? A . A ir from this source n a y contain oil odors, mists of oil o r water, particles o f rust or dirt from the air receiver or air lines, and in case of improper compressor operation there may be burning of the lubri cants w ith the form ation of carbon monoxide. 47. Q. W hat precautions should b e tak e n to lessen the d a n g e r from a ir contam ination in th e use of reciprocating type of air com pres sors? A. Good maintenance and care in operation of the compresor, tempera ture indicators on the outlet side o f compressor, and carbon monoxide detecting equipment or carbon monoxide alarms on the outlet side to give indication of the presence o f any carbon monoxide. Individual compressor units so constructed as to make generation o f harm ful gases impossible are desirable sources o f clean a ir for air-line respirators. The M S.A. Clean A ir Blower is designed to fill this need. 48. Q . W hat is a chem ical filter respirator? A. It is a respirator designed for removing gaseous constituents from the air breathed. The filtering materials in these respirators are usually . granules that react w ith the harmful constituents and remove them. 4S. Q . W h at is a m ec h an ic al filter re sp irato r? A . A mechanical filter respirator is a device th at removes by mechanical filtration the particles of harmful constituents from air th at passes through it. These devices include dust, mist, and fume respirators. Each o f diese types of mechanical filter respirators is designed to protect the wearer against the particular kind of matter to be dealt with. 50. Q- W hai is a U nited S tates B ureau of M ines "ap p ro v ed " m echani cal litter respirator? A . It is a respirator th at has officially passed die rigid test requirements of the U nit! States Bureau of M ines as outlined in th a t Bureau's A p proval Schedule N o. 21. 51. Q. W hat Is United S tates B ureau of M ines schedule No. 21? A . It is a publication that describes the requirements and tests that a respirator must meet in order to obtain the approval of die Bureau of 9 SC 030769 Mines. Free cop3 of this publication may be obtained upon request from the United States Bureau of Mines, W ashington, D. C. 52. Q . For w hat types of m echanical Slier respirators does the Bureau of M ines schedule No. 21 provide approval requirements? A. Schedule No. 21 provides approve) requirements for mechanical filter respirators for protection agatnst mechanically generated dusts (known as Type A respirator); fumes of various metals (Type B ): and mists such as those from chromic a d d aixf from spray coating in the absence o f harm ful vapors and gases (Type C ). Combinations of these types may also be approved. 53. Q. W ho m okes the approved tests? A . T he Bureau o f Mines makes the tests at its Pittsburgh Experiment Station where experienced personnel and complete laboratory facilities for dust investigations are available. 54. Q . W hat are the general perform ance requirem ents that a m echan ica l filter dust respirator must give in order to obtain th e ap proved of the Bureau of M ines? A . The general features of the performance requirements are: 1-- Dust-tight fit of the facepiece. 2-- Reduction of dust in the inhaled air below an amount that causes harm. . 3-- A resistance to breathing that is below that which produces discomfort. 4-- A satisfactory degree o f convenience, durability, and service. Coal Miner w a rm 5 COM FO RESPIR A TO R !0 SC 030770 1 55. Q. W h at is the size oi the d u st particles used b y the U nited S ta te s B ureau oi M ines in the approval tests oi respirators? A. T he dust piracies used in the tests are 95 7< below 1.7S microns and 505c below 0 <5 micron. These sue characteristics are very similar to those found m the atmospheres o f mines and industrial plants. i 5S. Q . W h a t se v e re d u st tillering a n d re sista n c e p e rfo rm a n c e ro u st a m echanical tiiter dust respirator give to pass the approved test? A. A ir chat contains fifty milligrams per cubic meter (approximately 300 to 500 million parades per cubic foot) o f dust o f the small sice specified by the Bureau of Mines is drawn through the respirator ar a rate of 32 liters a minute, or at approximately the rate at which air is breached by an average man doing work. The total amount of dust that leaks through the respirator m a 90 minute test period during which 2.S8 cubic meters o r 100 cubic feec of air are passed must nor exceed 3.0 milligrams or 0.0001 ounces. The resistance to inhalation i: when tested with air Bowing through the respirator a t 85 liters a minute must at no time exceed 2 inches of w ater column. This resis tance is below that which causes discomfort. 57. Q . A re the B u re a u oi M ines a p p ro v a l re q u ire m e n ts u n n e c e ssa rily exacting an d impractical? A . No. The approval requirements in schedule N o. 2 1 represent the mini mum protection that a respirator should give in order to protect the wearer adequately. iii i ? M 3 A . Cdtnfo Respirator used during grinding operations It SC 030771  i 1 58. Q . W hat a re the mast im portant features ai a respirator? ) A. t --Adequate respiratory protection. 4J 2--Comfort and convenience. 3 3-- Ease and cost of maintenance. 4 1 59. Q . W hat is th e Comfo R espirator? ' A . It is a particular type of respirator manufactured by the M ine Safety Appliances Company that is approved by the U. S. Bureau of Mines. It was the first respirator to pass this Bureau's approval tests. It has filters of specially treated cellulose for removing the dusts of very sm all size that are present in industrial atmospheres. T he filters are pro tected from damage or contamination by a metal covering and ere attached to both sides of an all rubber facepiece. It has a large filtering area and low resistance to breathing. 60. Q . H ow does the Comfo R espirator m eet the requirem ents for a d eq u ate respiratory protection? A . The protection afforded by the Comfo Respirator is certified b y the U nited States Bureau of Mines approval which it carries as a result of having successfully passed the approval te a s against dusts o f a particle size 95% of which are le s than t.78 microns and 50% less than 0.60 microns. This is the range of particle sizes usually found for mine and industrial dusts. 61. Q . W hat is m eant b y th e efficiency oi a respirator; cmd w h a t test facts concerning efficiency m ust b e k now n to determ ine ii a respirator gives ad eq u ate protection? A . The efficiency of a respirator is the percentage of the dust in the air that is retained an the filter. A t least three very im portant facts should be known in order to determine if a respirator, that has a reported high efficiency, also gives adequate protection: t-- The dust concentration used in determining the efficiency figure. 2-- T h at the particle size of the dust used in determining die efficien cy represents the size of the dusts found in industrial atmospheres. 3-- T hat the percentage inefficiency, or the amount of du st that leaks through, does not exceed that which is safe to breathe. 62. Q. H ow does variation in particle size effect the reliability oi a n efficiency value of a respirator? A . T he statem ent that a respirator is 98% efficient means little if th e particle size range of the dust tested is not given because d ie difficulty ` in removing dust increases as the particle size decreases so th at dusts below l to 2 microns are much more difficult to remove than the larger sizes, yet it is particles below 1 to 2 microns th at predominate in in dustrial and mine atmospheres and produce the harm ful effects. A respirator which would not effectively remove dust below 2 m icrons could be 9S% efficient provided the test was made against concentra tions that contain only a small amount of particles below 2 microns in she. 12 1 SC 030772 63. Q. H ow is the reliability of a n efficiency value a s a m easure of d u st protection affected by the concentration of dust in the air? A, A respirator may have high percentage efficiency and still ieak enough dust through the After to cause harm. For example, a respirator thar is 9T^i efficient against a concentration of J00 million particles of dust per cubic foot o f air (a nut unusual case) would leak i 5 million particles which u more than is considered a permissible amount of dust with a high silica content in the air breathed. The Bureau of Mines approval is given only ro respirators that do not leak enough dust to bring the dust m the air breathed above permissible limits. 64. Q . W hat is m eant b y comfort and convenience? A- The following factors arc elements of comfort and convtTuer.ce: 1-- Resistance to breathing 2-- Degree of impediment and encumbrance to vision and normal performance of wort. 85. Q. Should comfort an d protection be considered separately? A . No. Any acceptable respirator must give both adequate protection and an acceptable degree of comfort. 66. Q. How does the Comfo Respirator meet the comfort requirem ent? A . T he comfort of the Comfo Respirator is assured by its low breathing resistance, light weight, and lack of encumbrance to the wearer's vision and movement. M S.A. Comfo fU itirato r u-ore by [I'orSrr m crrcmic pfnnt 15 57. Q. W hat is m eant by cost of m aintenance? A . T he cost of maintenance is the expense involved in keeping the respira tor in an efficient, comfortable, and dean working condition- Low cost of replacement of Brers is an important element in this expense. G3. Q . How does the Comfo Bespirator meet the low m aintenance cast requirem ents? A . The law maintenance cost of the Comfo Respinuor is given by the low cost of the replaceable filters and the short time required for replacement. S3. Q. W hat is m eant by ease of m aintenance? A . By ease of maintenance is meant the ease with which a dust laden respirator can be restored to its initial high degree of efficiency and comfort through: 1-- Servicing. 2-- Replacement of filters. 3-- Sterilization. 70. Q . How does the Comfo R espirator m eet this requirem ent far e a se af m aintenance? A- The low cost of Comfo Respirator filters permits discarding of die dust laden filter and replacement w ith new filters. This avoids the denning of filters and provides a new and dean filter with the initial high degree of protection and comfort. 71. Q . How can respirators be sterilized? A- Scrub rubber and metal p a ra w ith soap and water. Rinse in warm water and immerse for 10 minutes fit a solution of formalin made by placing one part of 40% formaldehyde solution into 9 parts of water. Instead of the formalin solution. 1 part of carbolic a d d in 33 parts of water, or l part of Lysol in 50 parts or water, or S parts o f denatured alcohol in 3 parts of w ater may be used. All respirators should be thoroughly rinsed w ith w ater immediately after immersion in the sterilizing solution and put in a clean place to dry. 72. Q . H ow does the Comfo Respirator perm it e asy a n d thorough steril ization and cleaning of all parts? A . Owing to the low cost o f filters, these parts can be discarded and the entire remaining part of the respirator thoroughly washed and steri lized. A fter replacement of new filters the respirator is in its original clean and efficient condition. This permits daily sterilization o f all parts and avoids the growth of bacteria and danger o f contamination from parts that cannot be completely sterilized. 73. Q . How does the Comfo Respirator m eet the requirem ents of in d u s tries for respiratory protection? A . T he Comfo Respirator is certified by the United States Bureau of Mines Approval as giving adequate respiratory protection; it is com fortable and convenient; it is easily maintained and the cost of filter replacement is low. 14 SC 030774 Equipment for Protection from Dusts Manufactured by M ine Safety A ppliances Com pany M.S.A. COMPO RESPIRATOR Tbe M.5-A- Comfo Duet and M ist Respira tor is a mechanical filter rype respirator chat 09 developed to protect workmen from breathing dust such a* niica, coal. iron, asbestos. and orher air carded par' tides of the very small aes f o is d ui indus trial atmospheres. & will olio protect against the harmful liquid oust produced in chromium plating and the m*t o f vitreous eoacets. This respirator has been officially approved by the U. S. Bureau of Mines, Approval S'* . 2101. T he M.S.A. Comfo Lead Dust Respirator is identical in design th the Dust and Mit Respirator except the cellulose filters are specially treated for filtering out lead dusts of small particle sites. It u officially approved by the LT. S. Bureau of Stines. Approval No. HOT. M .SA. AIR LINE RESPIRATOR The M-SrA. A ir Line Respirator provides protection from gases, vapors. dusts, and fumes by providing the wearer with an ade quate supply of air for breathing require ments. Both the M.S.A. A ir Line Respirator and tbe M i A Abrasive M iA ' (shown later) have free-wheeling control valves to insure gainst accidental bumping and chang ing of air 3ow* aod a qutdc release connection in case tbe air supply foils or becomes un usable for any reason. 15 SC 030775 tf M.S.A. ABRASIVE MASK. \ i J | s .1 The M S A . Abrasive M ask is a light, comfortable, fresh an supplied un it_designed for rciw ratory protection Irom the high concentrations of fine dust produced by abrasive blasting with sand or shot, and for protection of the head and moulders from impact and abrasion by the High velocity rebounding parades, ft gives protection fiom dusts, fumes, and vapor** J I M.S.A. CLEAN AIR BLOWER i i 1 I \ \i i fhe 1 1 5 A. Clean A ir Blovcer is specially designed for iuppljtng ait that is m ol. dean . Lumidifted. and free from obnoxious or Harmful cases to air line respirators. sand blase mods, and helmets. I t is a rotary type m which water u used as a comprewor seal, oobns medium, humidifier, air washer, and dust remover. Tncre is oo mternal lubncat.on j ^ M flnA of A * air w ith oL grtaie, cc co n o o in au n g agent*. 16 fRIMTEO W U .S .* . SC 030776 SC 030777 SC 030778 Pertinent Questions and Answers Concerning Dusts 1. Q . W hat axe the u su al classifications of air-carried particles? A . A ir-earned particles are usually classified into three groups: 1-- Dusts 2-- Fumes 3-- Mists 2. Q. W hat are dusts? A. Dusts are mechanically generated particles resulting from such opera tions as dolling, blasting, crushing, and handling of rocks and minerals; sand-blasting; stone and granite cutting; grinding and polishing; and all sim ilar operations and processes. The greater percentage of particles of air earned dusts are below one micron m site with an average be tween 0.5-0.7 microns. 3. Q. W hat is a micron? A. A micron is a un it of measurement, one micron being equal to about 1/25,000 o f an inch o r in other words it would require 25,000 particles each one micron in site laid end to end to measure one inch. 4. Q. W hat is the sm allest particle that can be seen b y the naked eye? A. T he smallest particle visible to a person with average eyesight is about 100 microns in dimension. This is 1/250 of a n inch. 5. Q. How d o es this com pare w ith the size of the average particle found in air-bom industrial dusts? A. This is one hundred and fifty to tw o hundred times the site of the average particle found in industrial atmospheres. In other words, the particles o f dust o f significance from the standpoint o f health are only a small fraction o f the site th at is visible to the naked eye. S. Q. W hat range of particle sizes is important? A. T he particles below 5 microns are of most importance as dusts of larger size settle out of the air very quickly and are not likely to be breathed. In general the particles of dust found in industry are below one o r two microns w ith as much as ''095: below 0.5 or 0.7 micron. U nder some - conditions the size may be larger or smaller than this general a te range. 7. Q. W hat are fumes? A. Fumes are particles produced in chemical and metallurgical processes, welding, and similar operations, o r by the decomposition of chemicals by heat and combustion. T he average particle site is less than that of dusts. M ost fumes have an average particle site of 0.2-0.3 microns. The im portant harmful fumes are usually die fumes of metals or their compounds such as lead oxide, zinc oxide, arid cadmium oxide. O w ing to their small particle size; fumes are even more difficult to remove by filters than are mechanically generated dust i. & -T SC 030779 SC 030780 11. Q. W hat is a toxic dust? A. A toxic dust is usually considered to be the dust of a poisonous ma terial, such as lead and arsenic or their compounds, that produces injury to organs such as the circulatory system, heart, liver, kidneys, brain, and nervous system. W hen a poisonous dust is inhaled and deposited in the lungs, it dissolves and is earned by the blood to all organs and tissues. It m ay also be deposited in the mouth and throat by inhalation or contamination with dirty hands, and later swallowed and enters the body through the digestive tract. 12. Q. W hat is a nuisance dust? A. A nuisance dust is one that is often associated with an increase in respiratory diseases (such as. colds in the head, bronchitis, pneumonia, and tuberculosis). M any such dusts are discomforting and irritating . to the worker and may be harmful. They do not produce toxic effects or form fibrous tissue in the lungs. 13. Q . W hat Is a fibrosis-produeiag dust? A. It is one that through its action in die lungs causes a disease of the normal lung tissue and a replacement of this vital tissue w ith fibrous (scar) tissue. 14. Q . W hat is pneum oconiosis? A . It is a term applied to any lung disease arising from inhalation of dust. 15. Q . Wheel is silicosis? A. It is a disease o f the lungs in which the normal lung tissue is replaced by fibrous (scar) tissue due to breathing air that contains free silica dust (silicon dioxide, SiOs). 16. Q . C on silicosis b e produced by any substance other than, free s ilic a ? A . Silicosis is a specific disease caused only by breathing free silica. How ever, there are indications th at the presence of other kinds of dust and gases may influence the effect o f silica in the lung. 17. Q. W hat is m iners' pthisis? A. It is a term used frequendy to designate a condition of silicosis com plicated by the presence of tuberculosis. 18. Q. W hat is anthraco-sdlicosis (m iner's asthm a)? A . It is a chronic disease o f the lungs in which the normal lung tissue is replaced by scar tissue caused by breathing excessive amounts o f a mixture of silica dust along w ith coal dust. 19. Q . W hat is asbestosis? A . Ic is a disease o f the lungs in which the normal lung tissue is replaced by fibrous (scar) tissue due to breathing air that contains asbestos dust. SC 030781 20. Q. W hat are the principal factors in determ ining the health hazard from air-carried dust? A. The following factors arc usually important: 1-- Chemical composition of the dusc. 2-- --Am ount of dust in che air. 3-- Sue of the dust particles. +--Length of time of exposure. Zl. Q . W hat is m eant by chem ical com position oi a dust? A. A ll materials such as rocks and minerals are not what might be termed pure chemical compounds, but are mixtures of several chemical com pounds. The chemical composition is the kind and amounts of these v ar ious components. In the case of silica-bearing substances, the amount of silica present may vary from almost nothing to 100%. The amount of free silica present is obviously the important factor in the silicosis . producing properties of a dust. 22. Q . Is the chem ical com position oi the dust in the air the sam e as the su b stan ce th at is being drilled, handled, crushed, or processed? A. As most dust producing substances dealt with in industry contain more than one mineral component, some of these components will crush or disintegrate more easily than ocbers and thereby form a larger pro portion o f small parades. These smaller particles will tend to pre dominate in the air while other constituents being larger will settle out. For this reason, the composition of the dust in the air may vary greatly from the composition of the rock or mineral. 23. Q. W hat is ths im portance of the chem ical com position of a dust? A. T he chemical composition reveals the harmful constituents and their amount, and constitutes the basis for judging the harmful qualities of the dust. This information is an important factor along with con centration and tame of exposure in determining the hazard 24. Q. W hat are the im portant step s in determ ining the chem ical com position oi a dust? A . It is necessary to first obtain a sample that represents the dust in the air breathed, and then subject the sample to methods of analysis that ' are known to give accurate results for the constituents desired. 25. Q . How can a representative sam ple o i the dust in the air breathed be obtained? A. It can be obtained only by collecting the dust from the air. Samples of pieces o f rock or settled dust do not necessarily beat any dose re lation in composition to the dust Soaring in the air. 26. Q . H ow can a sam ple of sufficient size for chem ical an alysis be collected from the air? A . Collection from the air can be accomplished w ith dust collection devices such as the impinger, electrostatic precipitator or filter type of collectors -a-' SC 030782 27. Q. W hat m ethods a re g enerally used lor determ ination of the percent of free silica in dusts? A . 1-- By observing the action ot the small dust parades on light -with die aid of a special type of microscope. T his is known a t the petrographic method. 2-- By chemical analysis, 3-- By observing the action, of the particles on X-Rays. 23. Q. W hat a re the lim itations of the petrographic method? A. It is impossible by this method to examine individual particles below one o r tw o microns in a t e and smee most of the air-carried dust is below this a te range, one must rely on petrographic information obtained from particle sizes th at are above those o f primary significance 29. Q . W hat a re the Unritaiiann of the chemical method? A . T here is no known chemical method that is spedfic for free silica (SiOc) when this constituent is present w ith silicates. However, by observing the difference in the rate at which alica dissolves in certain acids as compared vvnh other constituents a rough estimate can be obtained for some dusts, b u t with others the method will be greatly in error. 30. Q. W hat a re the lim itationa of th e X-Ray method? A . T he X-Ray procedure can be used for making specific determinations of free silica in a very small sample such as 25 to 50 milligrams. The disadvantage of the method is that it requires very expensive ap paratus. 31. Q . W h at is m ean t b y size of particle; h a w is it expressed? A. T he size o f the parriclc is its largest dimension, usually expressed in microns. It has been stated by authonties that if all dust below one micron in size could be eliminated, nearly all dust disease w ould be eliminated. 32. Q . H ow co n the size of d ust particles b e determ ined? A . The size o f dust particles is measured by means of a microscope oc by projection of the dust particles on a screen similar in general principle to ordinary lantern slide projection. T he particles as seen m the microscope o r projected are then measured. 33. Q . H ow quickly d o es Ena d ust settle? A. It settles very slowly. In the table given below wit! he found the time in minutes estimated for silica dust of given sices to fall one foot in sbll air. Time in minutes to Size in microns fall one foot SC 030783 34. Q. Does a b sen ce of visible dust m ean ab se n c e oi fine dust? A. No. The operation may produce only fine dust or the visible dust may have disappeared owing to its rapid rate o f settling, leaving the invisible but harm ful dust in the air. 35. Q. W hat is m ean t b y d ust concentration.* how is it expressed? A , The concentration is the amount of dust suspended in a given volume of air. It is usually expressed in number of particles in a cubic foot o f air, or millions of particles in a cubic meter of air, or in a cubic centimeter. It m ay also be expressed as the weight of dust in a given volume of air as milligrams in a cubic meter or grains in a cubic foot. 36. Q. W hat Is the relation am ong these units oi quantity? A. Number o f cubic feet times .02832 gives number of cubic meters (m3) Number of cubic meters times 3).31 gives number o f cubic feet. Number of cubic feet times 28.317 gives number of cubic centi meters (cc.) Number o f milligrams times .001 gives num ber of grams. Number of grains times 64.80 gives number o f milligrams. Num ber o f grains times .00229 gives ounces (avoirdupois) 37. Q. How c a n th e concentration in particles p e r cubic centim eter b e converted to n um ber of p a rtid e s p e r cubic loot? A. M ultiply the num ber o f particles pet cubic centimeter by a million and divide by 3T.31 to get number of particles per cubic foot- 38. Q. How m an y particles of air-carried dust a re in one milligram weight of dust? A. It has been found that one milligram o f silica dust of the su e range present in industrial atmospheres contains about 200 to 300 million particles. 39. Q. W hat ap p aratu s an d methods are generally used lor determin ing dust concentrations? . A. The impinger and electrostatic precipitator are the instruments general ly used for this purpose. Details o f the instruments and methods can be found in publications of the United States Bureau of Mines and the United States Public Health Service. 40. Q. W hat is a n im pinger? A . It is a device by which air is drawn a t a definite rate of flow and at high velocity through a snail nozzle so directed as to strike the bottom of a glass flask which is partially filled with a liquid such as water, alcohol, or a mixture o f these liquids. T his high velocity action causes the dust partides to be " wetted" and retained m the liquid. Some o f this liquid is then examined under a microscope and a count of the dust parades present is made. T 41. Q. W hat is cm electrostatic precipitator? A. It's a. device by winch .nr to draw n at a definite rate of flow through a high voltage electrical field so arranged as to cause any dust to he re moved and deposited in a sampling tube. i~hc dust collected can be determined either by counting rhe number of particles with a micro scope or by weighing It is an efficient method but requires a source of electrical energy As with the unpmger, the electrostatic precipitator collects rhe dust continuous!'.- from a comparatively large volume of air and thus provides a sample that represents average conditions. It mayeven be used to collect a sample that is large enough for chemical analysis. 42. Q . H ow com e x p o su re b o d e te rm in e d ? A. Since exposure is a term th a t involves concentration, particle a re. chemical composition, and duration of time, it is necessary to determine all of these m order to properly evaluate the decree and extent of exposure. The time element requires an accurate i<-b analysis in which is recorded the amount of time spent by a workman at his various operations. T his record should, then be associated with the dust con centration, particle sire, and chemical composition of the dust at each operation and the average over all daily exposure determined. For Example: Summary of Dust Exposure of Lcyner Drillers m a Granite Quarry Activity- Average exposure in millions of particles per cubic foot. Hours spent in each activity Particle h e . (millions per cubic foot) Drilling......... .......... --. Changing drills.......... W atching drills.......... Broaching.----_--------Blowing off holes.... 215.4 9.8 3.0 6.0 108S.0 4 853.6 1 9.8 2 16.0 A 4.5 A 271.3 TotaL. 8 tlf.2 1155 2 particle hours m millions per cubic foot 144.4 million particles per ------ ----------------------------------- ---------------------cubic foot. Average expos kr --------------------------------- ure throughout the day. Tabic from U. S. Public Health Bulletin 217 by Bloomfield and OallaviUc 43. Q . W hat is a respirator? A . Any personal protective dim or designed to prevent the wearer from inhaling the harm ful'constituents in his surrounding atmosphere is called a respirator. " l'y * ! SC 030785 How ore the various types oi respirators Respirators arc classified as follows: 1. Air-supplied respirators. 2. Chemical filter respirators 3. Mechanical filter respirators. usually classified? W hat is a suppiied-air or car-line respirator? It is essentially a hose line thmugh which air that ts safe to breathe is conveyed to a facepiece worn hy the workman Air-tine respirators arc approved hy the United States Bureau of Mines under schedule No. 19 The air may be supplied from the compressed air line although pre ferably it should come from a separate blower unit designed to furnish air free from distasteful or harmful impurities. 46. Q . W hat harm ful or o bjectionable constituents m ight b e p resent in high pressure air as produced by a n ordinary reciprocating type of compressor? A ir from this source may contain <u! odors, mists o f oil or water, particles of rust nr dirt from the n r receiver or air iincs. and in case of improper compressor operation there may be burning of the lubri cants with the formation of carbon monoxide. 47. Q . W hat precautions should b e taken to lessen the d an g er from air contam ination in the use of reciprocating type oi air compres sors? A . Good maintenance and care in operation of the compressor, tempera ture indicators on the outlet side of compressor, and carbon monoxide detecting equipment or carbon monoxide alarms on rhe outlet side to give indication o f the presence of any carbon monoxide. Individual compressor units so constructed as to make generation o f harmful gases impossible are desirable sources o f clean air for air-line respirators. 48. Q . W hat is a n abrasive m ask? A . A n abrasive mask is essentially an air line respirator w ith a special hood for protection against high velocity particles in sand or shot blasting operations. 49. Q . W hat is a chem ical filter respirator? A . it is a respirator designed for removing gaseous constituents from the air breathed. The filtering materials in these respirators are usually granules that react with the harmful constituents and remove them. Chemical filter respirators are approved against light concentrations ot organic vapors under U. S. Bureau of Mines schedule No. 23. 50. Q . W h at is a m echanical filter respirator? A. A mechanical filter respirator is a device that removes by mechanical filtration the particles of harmful constituents from air that passes through it. These devices include dust, mist, and fume respirators. Each uf these types of mechanical filter respirators is designed to protect the wearer against the particular kind of matter to be dealt with. SC 030786 51. Q. What is a United Slates Bureau of Mines "approved" mechani cal tiller respirator? A . It is a respirator that has officially passed the rigid test requirements of the United States Bureau of Mines as outlined m that Bureau's A p proval Schedule No. 21. 52. Q. What are United Slates Bureau'of Mines schedules No. tS. 21 and 23? A. T hey are publications that describe the requirements and tests that respirators must meet in order to obtain the approval of the Bureau of Mines. Free copies of these publications may be obtained upon request from the United States Bureau of Mines, W ashington, D. C 53. Q. Who makes the approval tests? A. The Bureau ot Mines nukes, ihc tests at its Pittsburgh Experiment Station where experienced personnel and complete laboratory facilities for dust investigations are available. 54. Q, For what types of mechanical filter respirators does the Bureau of Mines schedule No. 21 provide approval requirements? A. Schedule No. 21 provides approval requirements for mechanical filter respirators for protection against mechanically generated dusts; fumes of various metals, and mists such as those from chromic acid and from spray coating in the absence of harmful vapors and gases. Combi nations o f these types may also be approved. 55. Q. What are the general performance requirements that a mechan ical filter dust respirator must give in order to obtain the ap proval af the Bureau of Mines? A. The general features of the performance requirements are: I-- Dust-tight fit o f the facepiece. 2 - Reduction of dust in the inhaled air below an amount that causes harm. -A resistance to breathing that is M o w that which products discomfort. +- - A satisfactory degree of cimvcmcncc, durability, and service. 56. Q. What is the size of the dust particles used by the United States Bureau of Mines in the approval tests of mechanical filter respirators? A- The dust particles used in the tests are below 1.78 microns and 50r a below 0 6 micron.. These size characteristics are very similar to those found in the atmospheres o f mints and industrial plants. 57. Q. What severe dust filtering and resistance performance must a mechanical filter dust respirator give to pass the approval test? A. A ir that contains fifty milligrams per cubic meter (approximately 500 to 500 million particles per cubic foot) o f dust of the small d ie 10 SC 030787 specified by the Bureau of Mines :s drawn through the respirator i t a rate of 52 liters a minute, or at approximately the rate at which air is breathed by an average n u n doing work. The total amount of" Just that leaks through che respirator in a 90 minute test period during which 2.88 cubic meters or !00 cubic feet of air arc passed must not exceed 5.0 milligrams or 0.0001 ounces. The resistance to inhalation when tested with air flowing through the respirator at 85 liters a minute must a t no tune exceed 2 Indies of water column. This resis tance is below that which causes discomfort. - 58. Q . Are the Bureau ot M ines approval requirem ents unnecessarily exacting and im practical? A. N o The approval requirements represent the minimum protection that a respirator should give in order to protect the wearer adequately 59. Q. W hat are the most important features of a respirator? A. 1--Adequate respiratory protection 2--Comfort and convenience. 5-- Ease and cost of maintenance BO. Q. W hat is m eant by the efficiency oi a respirator; and what test facts concerning efficiency must b e known to determ ine if a respirator g iv es adequate protection? A. The efficiency of a respirator is the percentage o f the dust in the air that is retained on the filter. A t least three very important facts should be known in order to determine if a respirator, that has a reported high efficiency, also gives adequate protection: 1-- The dust concentration used m determining the efficiency figure. 2 -- T hat the particle site of the dust used in determining the efficien cy represents the site of the dusts found m industrial atmospheres J--T hat the percentage inefficiency, or the amount of dust that leaks through, does not exceed that which i> safe to breathe Gi. Q. How d oes variation in particle size effect the reliability of an ' efficiency valu e of a respirator? A . The statement that a respirator is 98%- efficient mean- little if the particle site range of the dust tested is not given because the difficulty in removing dust increases as the particle size decreases so that dusts below 1 to 2 microns are much more difficult to remove than the larger sizes, yet it is particles below 1 to 2 microns that predominate in m dustriil and mine atmospheres and produce the harmful effect A respirator which would not effectively remove dust below 2 microns could be 98% efficient provided the test was made against concentra tions that contain only a small amount of particles bdow 2 microns in size. 11 SC 030788 62. Q. How is the reliability of cm efficiency value as a m easure of dust protection affected by the concentration of dust in the air? A . A respirator may have high percentage efficiency and stall leak enough dust through the filter to cause harm. For example, a respirator that is 97 /c efficient against a concentration of 500 million particles o f dust per cubic foot o f air (a not unusual case) would leak l i million parades which is more than is conadcred a permissible amount of dust with a high silica content in the air breathed The Bureau of Mines approval u given only to respirators that do not leak enough dust to bring the dust in the air breathed above permissible limits. 53. Q. W ho! is m eant by comfort and convenience? A. The following factors are elements of comfort and convenience' 1--Resistance to breathing. - -- Degree o f impediment and encumbrance to vision and normal performance o f work. 54. Q. Should comfort and protection bo considered separately? A. N o A ny acceptable respirator must give horh adequate protection ami an acceptable degree of comfort. 55. Q. W hat is m eant b y cost of maintenance? A . T he cost of maintenance is the expense involved in keeping the respira tor in an efficient, comfortable, and clean working condition. Low cost o f replacement of filters is an important clement in this expense. 66. Q. W hat is m eant b y ea se of maintenance? A. By case Df maintenance is meant the ease with which a dust laden respirator can be restored to its initial high degree of efficiency and comfort through: 1-- Servicing. 2-- Replacement o f filters. 3-- Sterilization. 67. Q. H ow can respirators b e Sterilized? A . Scrub rubber and metal parts with soap and water. Rinse in warm w ater and immerse for 10 minutes in a solution of formalin made by plaang one part o f 40% formaldehyde solution into 9 parts of water. Instead of the formalin solution, t part of carbolic acid in 33 parts of water, o r I part of Lysol m i0 parts of water, o r 8 parts o f denatured alcohol in 3 parts of water may be UsedAll respirators should be thoroughly rinsed with water imrocdiatcly aftcr immersion in the stenhang solution and put in a clean place to dry. SC 030789 SC 030790 Air Line Respirator Equipment M aHitjutturetl by Mine Safety Appliances Company M.S.A. A IR L IN E RESPIRATO R W ith "Cornfo" Cushion Facepiece M.S.A. ABRASIVE MASK M.S.A. "BLASTFOE" ABRASIVE HELMET H SC 030791 SC 030792 Castleman File on'/*"'1 ^ Doc # _L^_ wc = with cover letter or memo If DATE = 0, undated DATE = a r tic le __ a d v ____ a b s tra c t ___le tte r to e d ito r from : __ p e e r re vie w e d jo u rn a l ___ tra d e jo u rn a l __ n e w s p a p e r ____ m a g a z in e ___c o m p a n y jo u rn a l p u b lis h e d __ c o n fe re n c e ___p re s e n ta tio n ___ re p o rt F e d e ra l F e g is te r n otice __ N S C T ra n s a c tio n s u n p u b lis h e d r e p o r t__ o f a s b e s to s in s p e c tio n g o v e r n m e n t __ in sp e ctio n __ re p o rt ___ h e a rin g __ v b o o k e x c e rp t _ _ c h a p te r __ te s tim o n y __ le tte r __ m e m o __ n o te s o f __ c a ll___m e e tin g __ w a rn in g la b e ls __ p a te n t __ s a le s d a ta __ s a le s lite ra tu re __ re c o m m e n d e d p ra c tic e s m e e tin g ___ a g e n d a ___ m in u te s ___ a tte n d e e s le g a l__ a ffid a v it__ d e p o O R ___ te s tim o n y o f _______ Notes of Other BC or Castleman File on: wc = with cover letter or memo Doc# If DATE = 0, undated DATE = __ a r tic le ___a d v ____ a b s tra c t ___le tte r to e d ito r from : __ p e e r re vie w e d jo u rn a l ___ tra d e jo u rn a l __ n e w s p a p e r ____ m a g a z in e ___ c o m p a n y jo u rn a l __ p u b lis h e d __ c o n fe re n c e ___p re s e n ta tio n ___ re p o rt __ F e d e ra l F e g is te r n otice __ N S C T ra n s a c tio n s __ u n p u b lis h e d r e p o r t__ o f a s b e s to s in s p e c tio n __ g o v e rn m e n t in sp e ctio n report hearing __ b o o k ___ e x c e r p t____ c h a p te r ___te s tim o n y __ l e t t e r m e m o notes o f c a ll m eeting __ w a rn in g la b e ls __ p a te n t __ s a le s d ata __ s a le s lite ra tu re __ re c o m m e n d e d p ra c tic e s m e e tin g ___ a g e n d a ___ m in u te s ___a tte n d e e s le g a l__ a ffid a v it__ d e p o O R ___ te s tim o n y o f ________ (jg^m wc = with cover letter or memo Doc # If DATE = 0, undated DATE = article adv abstract letter to editor from: __ p e e r re vie w e d jo u rn a l ___ tra d e jo u rn a l __ n e w s p a p e r ____ m a g a z in e ___ c o m p a n y jo u rn a l p u b lis h e d __ c o n fe re n c e ___p re s e n ta tio n ___ re p o rt F e d e ra l F e g is te r n otice __ N S C T ra n s a c tio n s u n p u b lis h e d r e p o r t__ o f a s b e s to s in s p e c tio n g overnm ent inspv _V b o o k ___ e x c e r p t__ __ h e a rin g ,- ZAn t r i __ l e t t e r m e m o notes o f c a ll m eeting __ w a rn in g la b e ls patent sales data __ s a le s lite ra tu re __ re c o m m e n d e d p ra c tic e s m e e tin g ___ a g e n d a ___ m in u te s ___ a tte n d e e s le g a l__ a ffid a v it__ d e p o O R ___ te s tim o n y o f _______ le g a l________________________________________________ Notes of Other BC or Castleman File on: wc = with cover letter or memo Doc# If DATE = 0, undated DATE = Q> __ a r tic le ___a d v ____ a b s tra c t ___le tte r to e d ito r from : __ p e e r re vie w e d jo u rn a l ___ tra d e jo u rn a l __ n e w s p a p e r ____ m a g a z in e ___ c o m p a n y jo u rn a l __ p u b lis h e d __ c o n fe re n c e ___p re s e n ta tio n ___ re p o rt __ F e de ra l F e g is te r n otice __ N S C T ra n s a c tio n s __ u n p u b lis h e d r e p o r t__ o f a s b e s to s in s p e c tio n __ g o v e rn m e n t__ in sp e ctio n __ re p o rt ___ h ea rin g __ b o o k ___ e x c e r p t____ c h a p te r ___te s tim o n y __ le tte r __ m e m o __ n o te s o f __ c a ll___m e e tin g __ w a rn in g la b e ls __ p a te n t __ s a le s d ata __ s a le s lite ra tu re __ re c o m m e n d e d p ra c tic e s m e e tin g ___ a g e n d a ___ m in u te s ___ a tte n d e e s ? le g a l__ a ffid a v it J ^ d e p o O R testim ony of le g a l________________________ Notes of BC or Other