Document 99ZZ0yvpZXem9EaONwogaYQOp

FILE NAME: National Safety Council (NSC) DATE: 1961 Feb 3 DOC#: NSC132 DOCUMENT DESCRIPTION: NSC - Safe Practices Pamphlet - Respirators, Gas Masks, Hose Masks, and Breathing Apparatus - 1925 Article Destroyed in 1961 markto copy' 1 & l , Gas Masks, Hose Masks and Breathing Apparatus a- Safe Practices Pamphlet No. 64 R ^ Published by National Safety Council 108 East Ohio Street, Chicago. '3 -/3 This pamphlet is a compilation of experience in accident prevention. It must not be confused with Federal, State or insurance requirements, or with National Safety Codes. 1. The hazards to life and health from working in certain dusts, fumes and gases have long been recognized, and many law-en forcing bodies require that employ ers provide protection for workers exposed to these hazards. Progres sive emplojrers are giving careful consideration to numerous protec tive measures and are encouraging the development of respirators, gas masks and breathing apparatus de signed and built to meet industrial conditions. This is much better than endeavoring to use inadequate respirators, salvaged army and navy gas masks, or obsolete oxygen breathing apparatus. 2. The field of usefulness of each type of equipment is quite definite: (a) Respirators provide protec tion against certain forms of dust. It is difficult to obtain a complete seal against the .finest and most dangerous dusts, especially those containing silica. (b) Gas masks, properly selected for the conditions encountered, af ford good protection against certain fumes, gases or dusts which are poi sonous or have an irritating effect upon the nose and eyes, where the atmosphere contains sufficient oxy gen to sustain life. (c) Hose masks, providing fresh air through a hose from a safe dis tance, will protect the wearer from anj' conditions of gas, fumes or smoke that the exposed parts of the body may be able to withstand. (d) Self - contained o x y g e n b reath in g a p p aratu s is p a rticu larly useful where the atmosphere con tains insufficient oxygen to sustain life, or w here,the concentration of ferred to a gas mask. It does pro tect against coarse dust particles present in the air, but when a vast amount of fine particles and poison ous dusts are in suspension a consider able quantity of such dust adheres to the damp sponge or other filter used. While the amount of dust breathed is thus reduced the wearer cannot help but inhale vapors that are being gen erated by the contact of poisonous sub stances and the filter. (See Figure 2.) Courtesy, U. S. Bureaus of Mines Figure 1. Fireman wearing canister gas mask. This mask is provided with the nil-service canister, which gives protection against carbon mon oxide as well as several other gases. irrespirable gases exceeds two per cent. In cases where the hose mask is too cumbersome, the self-con tained breathing apparatus may be more adaptable. Respirators 3. The respirator is essentially mechanical filter. It can be used successfu lly w here insoluble dusts prevail. It is of no value, however, in reducing the ill effects of fumes or gases and should never be pre- Copyright, 1929, National Safety Council 4. Despite the fact that respirators have been known and used for a com paratively long time, the problem of protecting workmen from the effects of various kinds of dusts has often been better solved by the installation of exhaust systems. This subject is fully discussed in the National Safety Council's Safe Practices Pamphlet No. 32. Only a few of the manufactured respirators are recognized as effective .protective appliances. The chief ob jections to many respirators are: (1) some are too heavy, irritating the face ; (2) on others the straps around the head irritate the ears; (3) they are uncomfortable; (4) men cannot talk or chew or expectorate when wearing the respirator; (5) they do not fit the face accurately so that dust enters the mouth and nostrils between the res pirator and the face, or dust is blown into the eyes when exhaling; (6) they are not properly maintained where it is necessary to moisten or renew the filtering medium, and often this me dium is not properly cleaned; (7) workmen have a serious objection to awearing them due to the ridicule to which they are subjected; (8) they in terfere w ith wearing- go ggles ; and (9) the men often disregard hygienic suggestions because the respirator gives a false sense of security. PLAINTIFFS EXHIBIT M t ' 114 64 - ....9. The Bureau of Inspection of the New York State Industrial Commission has tested several com mercial respirators and the home made respirator described above. The greatest efficiency was ob tained with the home-made respira tor. Dust-laden air containing basic lead salt, was drawn through the filtering medium at a rate corre sponding to the am ount of air breathed by an average individual. Careful analytical tests revealed no lead drawn through th e home-made respirator. Other advantages of the home-made respirator a re : (1) it does not obstruct vision, (2) it can be washed if desirable, (3) it offers less incentive for one workman to appropriate the respirator of an other, (4) it does no t unduly in crease the expense by breaking, rusting, and wearing- out, (5) it does not cause excessive perspira^/- Courtesy, Youngstown Sheet & Tube Co. Figure 2. Two types o f manufactured respirators. The respirator on the right is the "Pig Snout" type, one of the earliest developed and which has been generally replaced by other types. The one on the left is more satisfactory. tion or irritaton of the cheeks, no4. chin, or ears, and (6) it can be/.norc easily arranged to fit various facial contours. The home-made respira tor will absorb perspiration in many 5. A respirator, just as any other 394' of the Bureau of Mines. It was instances, and thus avoid trouble article of clothing, should fit with rea found that all filter substances do some skin eruptions caused by some sonable comfort. It is possible to se not have the same retarding power dusts, notably that of fulminate of cure commercial respirators which are on dust, even when of equal poros mercury. light in weight and constructed of ma terials that are pliable enough to in sure an accurate fit to the various facial contours encountered among a large number of employees. Better maintenance of the filtering medium is possible only through supervision and through an appreciation of the neces sity for wearing the respirator prop erly, on the part of the workmen themselves. Improving the appearance of the respirator to eliminate the ridicule of fellow workers is desirable; ridicule is harder to combat than all other objections, 6. The area of the filtering me ity. Many filtering materials which offer great resistance to the pas sage of inspired air, permit the flow of dust quite freely, while others which offer but little resistance to breathing are found to be surpris ingly efficient. These experiments and research work have aided manufacturers of respirators to pro duce personal protection to meet special occupational conditions. If employers will fully explain their requirements, there should be little further difficulty in enabling work men to withstand dusty conditions of employment without harm. Gas Masks 10. Gas masks of the canister type should not be used in atmos pheres where there is a deficiency of oxygen (less than 16 per cent of oxygen). There are two general types of gas masks (not including self-contained breathing apparatus) ; (1) those having canisters which purify the air and (2) those with hose attached which introduces a fresh air supply. The latter style of mask is available with either a face piece or a helmet covering the entire head. dium must be as large as possible. The smaller the area of the medium, the greater will be the resistance to breathing. Other things being equal, increased resistance means smaller and fewer air passages through the me dium and increased velocity of air through the passages. An increase in velocity in turn tends to increase the amount of dust which is drawn through the respirator. 7. The Ignited States Bureau of Mines has completed experimental and investigation work on mediums suitable for respirator filters. The 8. A home-made respirator, (Fig ure 3) made of a piece of muslin 33 inches long by 5 inches wide, with absorbent cotton, as a filtering me dium, has found favor' with many men. A. respirator of this kind has been used successfully in many dif ferent plants. Absorbent cotton is an excellent filter when placed un der compression. I t is rapidly re placing a handkerchief--often dirty --which workmen tied around the nostrils and mouth. The device, is easy to make, and so inexpensive, if made in large quantities, that it is 11. The average gas mask is not cumbersome; it is simple and easy to wear. Special canisters can be secured to give protection from one gas or one class of gases, or to give protection against practically all kinds of gases. The mask illustrated in Figure 4 is equipped with an AllService canister. W hen workers are required to stay in one gaseous lo cation, and the hazard is from one particular kind of gas, it is usually more convenient and economical to provide a canister for th at specific gas. (See Figure 1.) results of these experiments are practicable to give each workman a 12. 'As a guide to the choice of now available in Technical Paper clean one every day or shift. the correct canister to be used in con- RESPIRATORS, GAS MASKS, HOSE MASKS AND BREATHING APPARATUS 3 nt-clion- with a gas mask, the..accom panying table, prepared from informa tion supplied by the U. S. Bureau of Mines and the Giemical Section of the National Safety Council, can be used authoritatively. 13. Gas masks are constructed largely of rubber and rubberized fabrics. Rubber hardens and cracks under the action of light and air, and fabric deteriorates if allowed to re main moist. Therefore, gas masks should be kept in a cool dry place and protected from light and air as much as possible. Manufacturers of gas masks generally provide wood or metal cases with each mask sold, and inform the buyer that the mask will last longer if kept in the original case when not in actual use. It is suggested that cabinets containing masks be sealed as shown in Figure 5. 14. It is difficult to estimate the life of a gas mask in use or in stor age, but under ideal conditions, the manufacturers claim that a mask should retain its usefulness for about two years. If not given proper care in storage, the life will probably not exceed one year. The rubber parts de teriorate rapidly when carelessly stored. TYPES OF CANISTERS FOR PROTECTION UNDER VARIOUS CONDITIONS Conditions Contents of Canister Color of Canister A. Protection in low concentrations Gas i masks with canisters containing 600 cubic of acid gases such, as chlorine centimeters or ^more of soda-lime or caustic soda formic acid, hydrogen sulphide, fused on pumice granules. The time of protec White nitrogen peroxidie,.sulphur diox tion decreases rapidity as the' concentration in ide, and the like (average 1 creases. Canisters of dry activated charcoal last per cent in air). only about one-fifth as long as soda-lime. B. Protection in high concentra Canister gas masks do not protect sufficiently well tions of acid gases (exceeding to assure safety. They should not be used. 2 per cent in air). C. Protection in low concentration Gas masks with canisters containing 600 cubic of organic vapors such as ani centimeters or . more of activated charcoal. The line, benzene, ether, toluene, time of protection decreases rapidly as the con Black gasoline, and the like (average centration increases. Canisters containing gas ab 2 per cent in air). sorbents other than activated charcoal are useleis. D. Protection in^ high concentra Canister gas masks do not protect sufficiently well tions of organic vapors (exceed to assure safety. They should not be used. ing 5 per cent in air). E. Protection against ammonia gas The above mentioned canisters containing lime, (not exceeding 3 per cent in soda, and charcoal absorbents do not protect air). against ammonia. Special canisters for that pur Green pose are required. These contain silica gel. The 3 per cent maximum cannot be long endured by the wearer of the mask, because of the severe skin irritation from ammonia gas. Fi Protection against carbon mon Special canisters containing Hopcalite, which oxide (not exceeding 3 per cent catalyzes the action of carbon monoxide with oxy in air). gen of air to produce relatively harmless carbon dioxide, protect against carbon monoxide. They Blue have some action on hydrogen sulphide and some other gases, but can be considered safe for use only in carbon monoxide. The masks protect in concentrations exceeding 3 per cent, but the in tense heat produced cannot be long endured. G. Protection against a combina Gas masks with canisters containing activated char Yellow tion of organic and acid fumes. coal and soda-lime. 15. After a mask has been used, it should be carefully wiped with a damp cloth and dried before beingput back in the case, special care be ing taken to see that there are not sharp folds or creases in the mask when put away. 16. When the same mask is used by several persons, it is always ad visable to clean and disinfect the mask after use. It is recommended that the mask, separated from the canister, be immersed and washed in a two per cent solution, of lysol and then dried in the open air with the lysol solution adhering. After the mask has been washed, the eye pieces should be thor oughly cleaned, as clean glass has less tendency to fog from moisture and permits better work. 17. It is impossible to estimate the life of a canister after use without testing it against gas, which, of course, renders it useless. If there is any rea son to believe that the canister is al most or entirely exhausted, a fresh canister should be.attached to the mask. The resistance to the flow of air may indicate the probable life in the carbon monoxide or All-Service masks. Man ufacturers deliver canisters with plug seals covering the bottom valve, and H. Protection against acid and or Gas masks with canisters containing soda-lime, ac Brown ganic vapors and ammonia. tivated charcoal and silica gel. I. Protection a g a i n s t dusts, smokes, and mists in combinanation with any of the above gases. J. Protection against mixture* tUhJCe above gguass eess IiUn air. (The All-Service Canister.) Canisters containing cotton-wool filters. Canisters containing two or more of the above mentioned absorbents protect against more than one gas or class of gases, but the total concen tration of mixed irrespirable gases in air should not exceed that allowed by the lowest maximum figure for any of the classes included. When more than one absorbent is contained in a canis ter the action of each is usually independent of the others and its capacity dependent upon its volume. Thus the capacity of the canister con taining several absorbents is less for a single gas than that of the canister filled only with the suit able absorbent. A contrasting black or white stripe on the canister indi cates the fil ter. Red with corks closing the hose nipple, un less the latter is attached to the face piece. When completely protected from the outside air, canisters should last a year, but when an excess of out side air is allowed to enter, they may deteriorate rapidly, especially canisters containing sodalime. Canisters in con tinuous use under a wide variety, of cir cumstances have shown a variation of life from a few hours to many weeks. 18. Canisters should be protec- ed, esp ecially from dam pn ess and air when not in use, and should be kept in a cool place. W hen a canisster has become water saturated, it should not be used again. W hen an assembled gas mask is stored for future use, the bottom opening of the canister should be closed with the plug stopper furnished with the canister. 19. The man who is to wear the mask should test the face piece to make sure that it fits and does not leak, before he enters a gaseous lo cation. To do this, the plug that seals the bottom opening is re moved, the mask put on and the h ead b a n d s a d ju s te d u n til th e mask fits closely, but comfortably. There should be no kinks in the tube be tween mask and canister. Resistance 4 SAFE PRACTICES PAMPHLET NO. 64 to natural breathing should be very slight. The bottom opening should be closed with the palm of the hand nd suction exerted with the lungs until the- face piece collapses. The tube and face piece should be ex amined at the same time to locate and life line- be used- in -every ..case where the wearer of a hose mask en ters a confined, irrespirable atmos phere. If desired, the man watching the life line may operate a blower to provide an ample supply of fresh air to the hose mask wearer at all times. 21. For many jobs the hose masks have several advantages. The mask is arranged so the air in the hose travels in one direction only, the exhaled breath passing through a valve in the face mask. The exhalation valve should be so constructed that it is normally closed and cannot under any condi tion permit the outside air to pass back into the mask. The Chemical W arfare Service has found that the so-called flutter valve such as was used on United States Army Gas Masks, is the best and safest for the variety of conditions encountered. Hose masks protect against all de ficiencies' of oxygen, since they are not dependent on the air surround Future 8. The home-made respirator, made of a piece of muslin with ab ing the wearer. They likewise pro tect against any concentrations of sorbent cotton as a filter, which has any kind of gas. so that they can be been very popular. used as long as the wearer is not working more than the hose length possible leaks. If there are no leaks, awav from an uncontaminated air he mask and the canister will hold supply. a vacuum for about 15 seconds. If th e gas mask is tight, the wearer can proceed, but he should enter the gas cautiously to see that the can ister is active. If the mask leaks, or if the canister is used up, fumes will be noticed (except in carbon mon oxide). When this evidence of fail ure is known, the wearer should im mediately return to fresh air and obtain a new canister, being sure to get the right canister for the gas to be encountered. Each person who learns to use a gas mask should undergo a physical examination, es pecially as to the condition of the lungs and heart. 22. W here hose masks are used, with a hose of greater length than 25 feet, it is recommended that an air blower be used to force a supply of air to the wearer. This is essen tial to overcome the friction of the hose. The air blower should always be of the centrifugal type, so in case of failure of the person operating the blower to maintain sufficient speed or to keep the blower in operation, the air supply to the person wearing the hose mask will not lie entirely cut off and air mav be drawn throueh the hose and pumo by the wearer. Enoutrh air mav he drawn through long lengths of hose in this way to permit the wearer Hose Masks to escape from an irrespirable atmos phere in safety and without removing 20. Hose masks afford protecthe mask. tion in any irrespirable atmosphere, but they are somewhat cumbersome, 23. In the presence of ammonia, and the length of the hose limits the hose masks will protect against any distance the wearer may move from concentration that the skin will bear. the source of fresh air. (See Figure 6.) If carbon monoxide is to be encoun T he masks are simplv a means of tered. a hose mask is probably safer providing ventilation for an individ to wear than a canister mask, as car ual entering an irrespirable atmos bon monoxide is odorless and taste p h e r e ;, th e y c o n s u m e n o c h e m ic a ls less. (See paragraph 19.) The hose ind are not limited in the length of mask weighs about five pounds, while time for which they may be used. It the vas mask weighs four to eight is- recommended th at a safety belt pounds, according to the size of the canister and style of. support for. the canister. There is practically no up keep or maintenance cost with a hose mask. 24. When 25-foot lengths of hose are coupled together the weight and stiffness of the hose may cause the couplings to unscrew. To prevent this, a lock that prevents free movement of any part of the coupling can be pro vided. 25. Compressor air should not be used for respiratory purposes unless no other source of air can be provided. Breathing Apparatus 20. Self contained oxygen`breath ing apparatus protects against de ficiencies of oxygen and also any con centration of gases and vapors. It is not dependent on surrounding air, so is especially useful in exploring and rescue operations. 27. Oxygen breathing apparatus was developed to assist in the rescue and recovery of persons in mines, fol lowing explosions or fires, in heavy concentrations of noxious gases. The United States Bureau of Mines has summarized the value of oxygen Figure 4. The All-Service gas mask, showing timer on the top of the can ister and a carbon monoxide detector. W ith this equipment, a man can enter a dangerous atmosphere, and soon know if the degree of concentration of carbon monoxide is or is not dan gerous for him to work in. Such a canister w ill be safe to wear in a t mospheres containing not more than 2 per cent of carbon monoxide. RESPIRATORS, GAS MASKS, HOSE MASKS AND BREATHING APPARATUS T-^2Jj5^;'-United'*~States--2Btireau 'of-Mmes.is.... prepared to give instructions to qualified persons without cost. When you next in spect the gas m ash/ seal the hox w ith a f sticker and m ark on it the date of inspec tion and condition ol the canister* Reproduction of N. S. C. Poster C 128 Figure 5. One good method of m ark ing gas masks when packed m the box for further use. breathing apparatus by comparison with conditions before its general use. Prior to the use of breathing apparatus many rescue men lost their lives and the A^ work of rescue was delayed by men rushing into the afterdamp. 28. Rescue crews have been killed y second explosions resulting from fires, making it hazardous to- ad vance the ventilation, whereas un der similar conditions the breath ing apparatus has been of great value in making it possible for men to reach and put out fires in advance of the ventilation. Breathing ap paratus is also used effectively in connection with the control and the re-establishment of ventilation fol lowing mine fires and explosions.. The training of a large number of miners in the use of the apparatus and in organized methods of pro cedure has brought about an im provement in discipline following mine disasters and fires. The great majority of the comparatively few deaths to persons while wearing breathing apparatus have been due to failure to use it properly. 29. In order th at the wearer can be assured of safety, a physical ex amination and a thorough course of instruction and training in.the use of the apparatus are needed. Th training should cover a period of several days under an experienced and competent instructor. The 30. The apparatus should be ex amined, tested and overhauled at intervals of about one month by skilled mechanics or other compe tent persons who thoroughly under stand the action and function of each'part. Failure to keep the ap-'s. paratus in perfect condition may ) jeopardize the life of the wearer.^.. (This also applies to gas masks and hose masks.) See Figure 7, for a n i excellent method of storing b re a th -^ ing apparatus. 31. Self contained breathing ap-'. paratus is available in two general. types: apparatus which will supply' oxygen for one-half hour and a p - ,^ paratus which will furnish an ample* ' supply of oxygen for two hours, v The half-hour apparatus weighs 15.' to 17 pounds and the two-hour ap?. paratus 30 to 45 pounds. W hen d is^f\; charged, they require renewal ofiSs* oxygen and chemical charges. Vari- j ous types of breathing apparatus are illustrated in Figures 8, 9, 10 and 11. 32. The work of the United States Bureau of Mines in devel oping, perfecting, and investigating the various types of breathing ap paratus has been of inestimable value to the mining industry. The valuable contributions of that or ganization have many applications in industry generally. It is, there fore, recommended that the Bureau of Mines be consulted whenever there is a need for breathing appar atus. 33. Several pamphlets on this subject have been issued by the Bureau of Mines. One pamph let entitled "Self-Contained Mine Rescue Oxygen Breathing Appara tus," is a valuable work for anyone interested in purchasing this type of equipment. The pamphlet can be secured from the Superintendent of Documents, Government Printing Office, W ashington, D. C.. at a cost of 20 cents. 34. The types of two-hour oxygen breathing apparatus commonly used in mine rescue work in the United States are described in that pamphlet. Con cerning other apparatus, the Ptfreau states: Two-hour mine rescue apparatus that de pends upon sodium peroxide, potassium per Courtesy, U. S. Bureau of Mines Figure 6. Hose mask w ith Tissot face piece. A helmet can be used instead of a face piece, but the latter is now preferred, by most persons. The hose i8 strongly fastened to a wide heavy web belt, which precludes pulling the wetsfe away from the face of the zoearer. oxide, or liquid, air for its oxygen supply has been used in Europe, but little is known of it here. The objections to apparatus that use peroxides as the source of oxygen sup ply are that much heat is freed with the oxygen, the rate of oxygen flow is hard to control, and the foaming of material tends to block the air ducts. Liquid air or liquid oxygen are not always available and cannot be stored for any great length of time. Half-hour, three-quarter hour, and onehour apparatus, so-called because they will supply oxygen for these periods of tin -v re useful in other industries. The B u r-jj[ of Mines does not use such apparatus in rescue and recovery work due to their time limita tions. A two-hour oxygen supply is desira ble in mine rescue work. Several types of half-hour oxygen breath ing apparatus that are on sale in the United States resemble the Fluess-Proto, the Paul, the Gibbs and the Braeger apparatus in con struction and operation. Tests like those run on two-hour apparatus to see that they are air-tight and to see. that they are in good working condition, should be run on half-hour apparatus before they are used in bad air. Half-hour apparatus is useful at plants where employees work in irrcspirable air for short periods, but it should be used only by men thoroughly trained in its use. 6 SAFE PRACTICES PAMPHLET NO. 64 ....n.... The. -apparatus...should, have, a release valve, operated By hand or automatically, at some point in the circulatory system of the apparatus for releasing to the outside air when desirable part of th e air in the circu latory system of the apparatus. It should not be possible for an apparatus wearer to draw outside air through this valve. o. I f the apparatus is equipped with high-pressure oxygen bottles, these should meet the test requirements of the Interstate Commerce Commission. I f there is a safety cap attached to the main bottle valve of the apparatus bottle or bottles holding highpressure oxygen, this safety cap should have the usual disk and in addition be filled with a metal that fuses at about 94 C. This fusible metal should not extrude from the safety cap under a pressure of 150 at mospheres. p. All apparatus should have gages for recording time or pressure of oxygen sup ply ; such gages should be of tested accuracy and should be placed on the apparatus where they can be read easily ,by the wearer. The flow of oxygen to the gage should be con trolled by a gage valve placed so that it can be readily manipulated by the wearer independent of the circulatory system of the Courtesy, Ford Motor Company apparatus. Figure 7. A good way to store breathing apparatus when not in use, N ote the cylinder of compressed oxygen, ready to recharge individual oxygen bottles on the apparatus. q. When the oxygen supply of the ap paratus is controlled by automatic devices, these should adjust themselves readily to the wearer's needs. 35. Two-hour breathing apparatus; g. The apparatus, when worn in irre to be safe and efficient, should meet the spirable atmospheres, should supply enough following requirements, according to oxygen to its wearer for not less than 2 hours without recharging. However, "half- the Bureau of M ines: hour" apparatus may be used for certain a. The amount of oxygen or air supplied auxiliary purposes in rescue work under ground, if these apparatus pass the tests for by the apparatus should meet the needs of two-hour apparatus, with the exception of r. The main bottle valve of the highpressure oxygen bottle or bottles should be so made that an apparatus wearer can not screw the valve stem entirely out of the valve. The main bottle valve should also have devices that will enable the ap wearer to lock the valve open. j ' the wearer at all times. The reducing valve of every breathing apparatus which aims to deliver oxygen at a uniform rate should be adjusted to supply not less than 2 liters. (122 cubic inches, or about 2 quarts) of oxygen per minute. those on oxygen and regenerator capacity. s. Any apparatus equipped with1_ h . . The apparatus should be of a designbreathing device should have a saliva ... that uses a mouth-breathing device or other and a firmly fitting nose clip. The saliyi face attachment that when properly adjusted to the wearer's face can not have more than 250 cubic centimeters of dead space inside, b. Regenerating material, if used, should including the tubes or connections attached absorb so much carbon dioxide from the up to the inhalation and exhalation valves. exhaled air that there will be not more than 2.5 per cent at any time in the inhaled air. The average carbon dioxide content in in haled air should not be more than 1 per cent during any 2 hour test period. ' i. A fully-charged apparatus complete with a headpiece should not weigh more than 40 pounds. The lightest weight com patible with safe and durable construction is desirable. . c. Apparatus should be free from me chanical obstructions in order that the wearer may breathe freely at all times. The resistance of the apparatus as a whole to the passage of air will show whether circu lation is free or obstructed. The highest resfcance of an apparatus should not exceed inches water gage. d. The temperature of the inspired air should not exceed a maximum of 110 F. when that of the external air does not e x ceed 85 F. A much lower temperature than 110 F. for the inspired air is desirable. c. The apparatus should be durable and all vital parts protected to prevent material damage or rapid wear. f. Every oxygen breathing apparatus should have a by-pass .valve which permits a free flow of oxygen or air from the oxy gen or air container to the circulatory sys tem of the apparatus, independent of the reducing valve. j. The mechanical construction of the apparatus should be such that every part can be tested, inspected and repaired by persons skilled in such work. All parts which need sterilizing should be readily accessible. k. All parts of the apparatus subject to, or liable to be subject to, pressures higher than 5 pounds per square inch should be of such construction or equipped with such devices as will insure the wearer's safety. l. The inhalation and exhalation com partments of apparatus equipped with a breathing bag or bags or their equivalent, should have a combined capacity of at least 9 liters (488 cubic inches or about 8 quarts) ; however, if a breathing bag with but one compartment is used it should have a capacity o f1not less than 5 liters (305 cubic inches or about 5 quarts). m. The apparatus should have no zone of constant negative pressure in its circula tory system. Courtesy,-U. S. Bureau of Mines Figure 8. The McCaa half-hour self contained oxygen breathing apparatus. MASKS, HOSE MASKS AND BREATHING APPARATUS 7 compressed-;..a i r .... a p p a r a tu s --could probably be devised and might be serviceable, although it would prob ably be rather heavy and expensive. 37. In Great Britain several types of liquid oxygen apparatus which do have regenerative features have been officially approved by the B rit ish Mines departm ent for use in mines. This type of apparatus is preferred to the self-contained breathing apparatus on account of its coolness. Such apparatus has not been sold in this country, partly because of the necessity of install ing oxygen liquefying apparatus at the mine or station, but they may be used where liquid oxygen would be utilized for other purposes also. Special Considerations 38. No particular industry or oc cupation except the petroleum, in Courtesy, Youngstown Sheet & Tube Co. Figure 9. The Draeger two-hour self contained oxygen breathing apparatus. dustry has had an unsatisfactory ex perience with gas masks and breath ing apparatus. The reason for this is the action of oil vapors upon the apparatus itself. The petroleum trap should be so designed that outside air vapors have penetrated rubber parts cannot be drawn through it. and breathing apparatus at times t. Oxygen used in breathing apparatus w ith fatal results. The breathing should have at least 98 per cent of oxygen, bags of both half-hour and two- no hydrogen, and not more than 2 per cent hour apparatus are now covered of nitrogen, with traces of argon. with heavy rubber, which reduces Compressed A ir Helmets chances of loss of life of the wearer. After use, the breathing bags should be aired in fresh air for at least six 36. Persons not familiar with thehours to rid them of absorbed mix problems to be encountered in irre tures before further use. spirable atmospheres and with the need for apparatus to work safely 39. Crude petroleum is a most in such locations have, from time to complex combination of vario u s time, expressed the opinion that an apparatus supplying compressed air to the wearer should be the most efficient one of all. Authorities are df the opinion, however, that the less said about the compressed air or liquid air helmets, the better, for they are not designed to give a full supply of oxygen for a predeter mined period, and they are not sup plied with regenerative features. In ordinary breathing a matv inhales and exhales from six to seven liters of air per minute during rest, and 60 to 70 liters of air per minute dur ing vigorous physical exertion. It' therefore appears utterly impos sible, on account of the weight of , the air and necessary containers, for a man to carry with him enough of either com p ressed or liquid a ir to have entirely fresh" air each breath for any length of time. For service Courtesy, U. S. Bureau of Mines Figure 10. The Paul tw o-how self up to a maximum of ten minutes, a contained oxygen breathing apparatus. Courtesy, U. S, Bureau of Mines F ig w e 11. The Gibbs tw o-how selfcontained oxygen breathing apparatus. hydrocarbons and various impuri ties. The different compositions of the oils have different effects upon the workers. W here natural heavy oils are present, asphyxia from gas is unknown, whereas with light oils, suffocation may be frequent. An analysis of gases at a petroleum re finery may disclose all of the following gases in various proportions: Carbon Dioxide. Hydrogen Sulfide. Oxygen. Carbon Monoxide. Nitrogen. Hydrogen. Unsaturated Hydro-Carbons lene, Propylene, etc.). Saturated Hydro-Carbons thane, Ethane, etc.). (Ethy (Me 40. Some of the petroleum operat ing men question the value of gas., masks in the presence of a small quantity of petroleum vapors, as at the manhole of a storage tank or at the wells in the producing field. The chief reason for apprehension is the length of life of the contents of the canister. This is indeed a very important ques tion fo r the fum es o f som e petroleum s suffocate a person very quickly. The hose mask is believed to be safer for such use. 8 SAFE PRACTICES PAMPHLET NO. 64 H....... 41. The hose type of mask has been very efficiently and very satisfactorily used as protection in the petroleum industry. Several of the failures of these masks have occurred because the hose has been allowed to lie in the sludge and the oil. The hose should be either tied to some object to keep it from contact with oil in any form, or a sleeve of ordinary garden rubber hose should be used. The breathing hose is usually % inch in diameter, and garden hose of l y i inches in diameter can be used for a sleeve. ...42. The Bureau of Mines has pub- lished Technical Paper 348, entitled "Gas Masks for Gasoline and Petro leum Vapors." It considers the various methods of respiratory protection in the petroleum industry and the effec tiveness of the three types of personal protection: canister gas masks, hose masks, and oxygen breathing ap paratus. /f CKNO WLEDGMENT This Safe Practices Pamphlet was drafted by J. M. Sandel and revised by R: H . Ferguson, Safety Engineer on the headquarters staff of the National Safety Council. The Council acknowledges the valuable assistance received in the preparation o f this pamphlet from the members of the safe practices conference committee, and special assistance received from the manufacturers and representatives of the devices described in the pamph let and the engineers and chemists of the Experiment Station o f the United States Bureau of Mines. R-6/29-3M i V r 9