Document 10j8yqwB266VQ2Qdezwgv8905

FILE NAME: Allis Chalmers (ALL) DATE: 1959 Nov DOC#: ALL010 DOCUMENT DESCRIPTION: American Standard Safety Code for Head, Eye and Respiratory Protection Reg. U.S. Pat. Z2. 1- 195S Revision 01 Z2-I938 UDC 614.891/ American Standard Safety Code for Head, Eye, and Respiratory Protection ;* r.v.. Sponsors Department of the Navy National Bureau of Standards U.S. Bureau of Mines MAY 141963 LIBRARY Approved November 27, 1959 AMERICAN STANDARDS ASSOCIATION INCORPORATED American Standard Registered United States Patent Office An American Standard implies a consensus of those substantially concerned with its scope and provisions. The consensus principle extends to the initiation of work under the procedure of the Association, to the method of work to be followed, and to the final approval of the standard. An American Standard is intended as a guide to aid the manufacturer, the consumer, and the general public. The existence of an American Standard does not in any respect pre clude any party who has approved of the standard from manufacturing, selling, or using products, processes, or procedures not conforming to the standard. An American Standard defines a product, process, or procedure with reference to one or more of the following: nomenclature, composition, construction, dimensions, tolerances, safety, operating characteristics, performance, quality, rating, certification, testing, and the service for which designed. American Standards are subject to periodic review. They are reaffirmed or revised to meet changing economic conditions and technological progress. Users of American Standards are cautioned to secure the latest editions. Producers of goods made in conformity with an American Standard are encouraged to state on their own responsibility in advertising, promotion material, or on tags or labels, that the goods are produced in conformity with particular American Standards. The inclusion in such advertising and promotion media, or on tags or labels, of information concerning the characteristics covered by the standard to define its scope is also encouraged. \ \ -I r 'I Published by AMERICAN STANDARDS ASSOCIATION INCORPORATED 10 East 40th Street, New York 16, N. Y. Copyright 1960 by American Standards Association, Incorporated Universal Decimal Classification 614.891/.894 PRINTED IN U.S.A. S1M163/3 ith its er the proval sumer, ct pre- using to one ranees, nd the ised to ndards ged to labels, elusion :erning Foreword (This Foreword is not a part of American Standard Safety Code for Head, Eye, and Respiratory Protection, Z2.1-1959.) The first edition of this code was completed in the fall of 1920 and issued early in 1921. It was prepared with the cooperation of an advisory committee of 19 men who had been selected because of their interest in and knowledge of the subject and as being typical representatives of the interests most closely concerned. The code was developed from a set of safety standards originally prepared in cooperation between the War and Navy Departments and the National Bureau of Standards. The second edition was issued in 1922, after revision by a sectional committee organized under the procedures of the American Standards Association, and was published as National Bureau of Standards Handbook H2. The scope of the Z2 project was enlarged to include respiratory protection because of the many processes where simultaneous protection of lungs and eyes was needed, and a ^revision was pub lished in 1938 as National Bureau of Standards Handbook H24. In 1946 the sectional committee was reconvened and started work on a revision. A subcom mittee on eye protection was organized under the direct supervision of the National Bureau of Stand ards; a subcommittee on respiratory protection was organized under the supervision of the U.S. Bureau of Mines; and a subcomittee on head protection was organized under supervision of the Department of the Navy. All parts of the standard had to be reviewed and brought up to date in order to include new materials and devices which had been developed since 1938, particularly the use of plastics for eye protection. Suggestions for improvement gained in the use of this standard will be welcomed. They should be sent to the American Standards Association, Incorporated, 10 East 40th Street, New York 16, N. Y. The committee that developed this standard is as follows: D r L eonard Green b u rg , Chairman R . L. L loyd, Secretary J % % b i * 4 % 1 Tj sa i Organization Represented Name and Business Affiliation American Ceramic Society...............................................................J ohn P aff, Ray-O-Vac Company J. Earl Duncan, Pittsburgh Plate Glass Company (Alt) American Conference of Governmental Industrial Hygienists.. .R obert M. Brown, St. Louis Health Division American Foundrymen's Society.....................................................J. W. Young, International Harvester Company American Gas Association........ .......................................................Edward C. Baumann, Public Service Electric and Gas Company American Industrial Hygiene Association..................................... H. H. Schrenk, Industrial Hygiene Foundation of America W. E. McCormick, The B. F. Goodrich Company (A lt) American Society of Mechanical Engineers................................. T heodore F. H atch, University of Pittsburgh T homas A. W alsh, J r, American Optical Company American Society of Safety Engineers........................................... Charles W. W yman, Western Electric Company, Inc W. F. Scholtz, Allis-Ohalmers Manufacturing Company (Alt) American Welding Society............................................................. Frederick C. Saacke, Air Reduction Company, Inc Associated General Contractors of A m erica............................ Arth u rL. Schmuhl Association of American Railroads.................................................M. B. Clayton, Southern Railway System Association of Casualty and Surety Companies........................... W illiam M. P ierce, Employers Liability Assurance Corporation, Ltd I V. 0 . Bohn, The Employers Group (Alt) Bausch and Lomb Optical Company...............................................Gordon Taylor I. B. Lueck (A lt) General Services Administration........................................... ... .J ohn F. K irby Granite Cutters' International Association of America................EDWARD MEADE Industrial Medical Association.........................................................Carl Dernehl, Union Carbide Corporation L. H olland W hitney, American Telephone and Telegraph Company (A lt) Organization Represented Industrial Safety Equipment Association International Association of Governmental Labor Officials, International Association of Machinists............................. International Brotherhood of Boilermakers, Iron Ship builders, and Helpers of America................................ Metropolitan Life Insurance Company............................... National Association of Mutual Casualty Companies........ National Bureau of Standards............................................. National Electrical Manufacturers Association,............... National Foundry Association............................................. National Safety Council........................................................ National Society for the Prevention of Blindness, Pennsylvania Department of Labor and Industry Telephone Group...................................................... U.S. Bureau of Mines, Department of the Interior.. . . U.S. Department of Labor, Bureau of Labor Standards, U.S. Department of the Navy......................................... U.S. Post Office Department........................................... U.S. Public Health Service............................................ Member-at-Large ............................................................ Name and Business Affiliation . .D arrell E. Albert, Mine Safety Appliances Company F, R. Davis, Jr, Davis Emergency Equipment Company, Inc G H. Gallaway, American Optical Company S. C. H erbine, Ray-O-Vac Company A. F. P armelee, United States Safety Service Company V. P. Gopcevic, Industrial Safety Equipment Association (Alt) . .M orris K leinfeld, New York State Department of Labor Craig H. H aaren, New Jersey Department of Labor and Industry (Alt) ..W . G. F linn W illiam Dameron (Alt) . . J ohn V. K earney . . J. W illiam F ehnel . ,E. G. Meiter, Employers Mutuals of Wausau J. C. Stennett (Alt) . . R alph Stair R. L Lloyd (Alt) E. K. P lyler (Alt) ..H . W. Speicher, Westinghouse Electric Corporation ..C . T. Sheehan . .K arl L. D unn, Coming Glass Works L. W. H acerup, Lumbermen's Mutual Casualty Company (Alt) . . L eonard Greenburg, Commissioner of Air Pollution of the City of New York J ames E. O'N eil (Alt) . .T homas A. Oravecz -Erle S. Miner, American Telephone and Telegraph Company Charles W. W yman, Western Electric Company, Inc (Alt) .'.S. J. P earce Lawrence B. Bercer (Alt) . . Sheldon W. H oman William G. Griffin (Alt) . . H. L. M athews R. W. W ebster ( Alt) . . Edward B. Landry . .D onald J. Birmingham ,. .S amuel R enshaw, Ohio State University Company it Company, Company Issociation nt oi Labor Labor and ition ition of iph iy, Ine Contents 1. Purpose and Scope ............................................................................................................................... 7 1.1 Purpose ............................................................................................................................................. 7 1.2 Scope ......................... ...................................................................................................................... 7 2. Exceptions ............................................................................................................................................... 7 3. Definitions ............................................................................................................................................... 7 3.1 General Inform ation................................. ............................................................................ 7 f 3.2 Specific Definitions ........................................................................................................................... 7 4. General Requirements ........................... .......................................... ............................................... 10 , 5. Head P ro tectio n ....................................................................................................................... 10 5.1 Hats ................................................................................................................................................... 10 5.1.1 Types and C lasses...................................................................................................................... 10 5.1.2 Materials ............................... .......................................... ......................................................... 10 5.1.3 General R equirem ents............................................................................................................. 10 5.1.4 Detailed Requirem ents.............................................................................................................. 11 5.1.5 Physical Requirements and Methods of T e s t.................................................................... .. 12 5.1.6 Selection of Head-Protective D evices..................................................................................... 13 5.1.7 Training A id s ............................................................................................................................ 13 5.1.8 Marking ..................................................................................................................................... 15 5.2 Helmets and Hand S h ield s......................... . . . .............................................................................. 15 5.2.1 function ...................................................................... ............................................................. 15 5.2.2 T y p e s ................................................................................................................................... 15 5.2.3 Styles .......................................................................................................................................... 15 , 5.2.4 Detailed Requirem ents........................................................................................................... 15 5.2.5 Marking ............................................................................................................................ 17 5.3 Face S hields................................................... 17 5.3.1 Function ..................................................................................................................................... 17 5.3.2 Intended U se s............................................................................................................................ 17 5.3.3 Styles and Types ..................................................................................................................... 17 i 1 \ 5.3.4 Materials ..................................................................................................................................... 17 5.3.5 General R equirem ents.............................................................................................................. 17 5.3.6 Detailed Requirem ents............ ................................................................................................. 18 f 5.3.7 Marking ..................................................................................................................................... 18 5.3.8 PhysicalRequirements and Methods of T e s t........................................................................ 19 6. Eye Protection ........................................................................................................................................... 19 i 6.1 Styles and Functions of Protectors ............................................................................................... 19 6.1.1 Goggles, E yecup........................................................................................................................ 19 T. 6.1.2 Spectacles, Metalor Plastic F ra m e ........................................................................................... 20 6.1.3 Goggles, Flexible F ittin g .......................................................................................................... 22 6.1.4 Goggles, Plastic Eyeshield......................................................... 22 6.1.5 Spectacles, Plastic Eyeshield................................................................................................... 22 6.1.6 Goggles, Foundrymen's .................... 22 6.2 Materials and Methods of Test of Protectors................................................................................. 23 6.2.1 M aterials.................................................................................................................................... 23 6.2.2 Disinfection .............................................................................................................................. 23 6.2.3 Corrosion R esistance................................................................................................................ 23 6.2.4 Water Absorption .................................................................................................................... 23 6.2.5 Flammability ............................. 23 6.3 L en ses.................................................................................................................................................. 23 6.3.1 Types of L enses........................................................................................................................ 23 6.3.2 General Requirements .................................... 24 6.3.3 Detailed Requirem ents..................................... 24 6.3.4 Methods of Test and Examination of L enses........................................................................ 24 7. Respiratory Protection .......................................................................................................................... 27 7.1 Classification of H a z a rd s................................................................................................................ 27 7.1.1 Oxygen Deficiency.................................................................................................................... 27 7.1.2 Gaseous Contam inants.............................................................................................................. 27 7.1.3 Particulate Contaminants (Dusts, Fumes, Smokes, Mists, F ogs)........................................ 28 7.1.4 Combination of Gaseous and Particulate Contaminants.................................................... 28 7.2 Classification of Respiratory Protective Devices ......................................................................... 28 ,,7.2.1 Atmosphere-Supplying Respirators ....................................................................................... 28 7.2.2 Air-Purifying Respirators . . ................................................................................................... 30 7.3 Requirements for R esp irato rs..................... ....................................................................... .. 33 7.4 Selection of R espirators................................. 34 7.4.1 General Considerations ............................................................................................................ 34 7.5 ,Use and Maintenance of R espirators............................................................................................. 36 7.5.1 General Considerations ............................................................................................................ 36 7.5.2 Precautions To Be Taken in the Use of Respirators .......................................................... 36 7.5.3 Instruction in Use of Respirators.......... .......................... 39 7.5.4 Maintaining, Cleaning, Disinfecting, and Storing R espirators.......................................... 40 Tables Table 1 Comparative Hat and Cap S iz es............................................................................................. 15 Table 2 Transmittances and Tolerances in Transmittance of Various Shades of Filter Lenses.. 26 Table 3 Selection of Eye- and Face-Protective Devices ................................................................ 27 Table 4 Color Code for Gas-Mask C anisters..................................................................................... 31 Table 5 Selection of Respiratory Protective D evice......................................................................... 35 Figures Fig. 1 Brinell Hardness Penetrator Assembly.................................................................................. 14 Fig. 2 Dimensions To Be Measured in Heat Deformation Test .................................................... 21 Fig. 3 Apparatus for Heat Deformation T e s t..................................................................................... 21 Appendix for Section 6 A l. Visible-Light Transmission and Haze T e s t................................................................................... 43 A2. Water Absorption Test (For Weight and Dimensional Charges) ............................................ 44 A3. Selection of Shade Numbers of Welding Filters ............................. 45 A4. Maintenance and Disinfection of Eye Protectors ....................................................................... 45 A5. Fitting of Goggles and Spectacles................................................................................................. 45 Z2.1 HEAD, EYE, AND RESPIRATORY PROTECTION 27 Table 3 Selection of Eye- and Face-Protective Devices Hazard Involved Relatively large flying objects Dust and small flying particles Dust and wind Molten metal Gases, fumes, and smoke Liquids Reflected light or glare Injurious radiant energy (moderate) Injurious radiant energy (intense) Protected Eyes, Face Eyes, Face Eyes Eyes, Face Eyes, Face Eyes, Face Eyes Eyes Eyes, Face Permissible Protective Devices Type Reference Goggles Spectacles Face shields 6.1.1, 6.1.4, and 6.1.6 6.1.2, 6.1.5 5.3.3 Goggles Spectacles Face shields 6.1.1, 6.1.4, and 6.1.6 6.1.2, 6.1.5 5.3.3 Goggles Spectacles 6.1.1, 6.1.4 6.1.2, 6.1.5 Goggles Spectacles Face shields 6.1.1, 6.1.4, and 6.1.6 6.1.2, 6.1.5 5.3.3 Goggles 6.1.3, 6.1.4 Goggles Face shields Goggles Spectacles Goggles Helmets Hand shields Face shields Helmets Hand shields 6.1.3, 6.1.4 5.3.3 6.1.4 6.1.2, 6.1.5 6.1.1 All described in 5.2 All described in 5.2.4.2 5.3.3 (must include crown protector and chin protector) All with spectacles described in 6.1.2 All with spectacles described in 6.1.2 7. Respiratory Protection 7.1 Classification of H azards. Hazardous at mospheres fall into the following broad groupings: Oxygen deficiency Gaseous contaminants: Immediately dangerous to life Not immediately dangerous to life Particulate contaminants (dusts,fumes,mists, fogs) Combination of gaseous and particulate contam inants Immediately dangerous to life Not immediately dangerous to life 7.1.1 O xygen D eficiency. The oxygen content of normal air is about 20.9 percent by volume. Atmospheres in confined spaces such as wells, mines, holds of ships, tanks, and burning buildings may contain a lower percentage of oxygen because of d ilu tio n o r displacem ent of the a ir by o th er gases or vapors, or because of the loss of oxygen by its reaction with, or absorption by, other substances. When the oxygen content of the air is about 16 percent, the flame of a safety lamp will be extin guished. Below this concentration, a person b re a th ing the air exhibits symptoms ranging from increased volume of breathing and acceleration of pulse rate to unconsciousness and death, depending on the oxygen content of the air and the degree of his physical activity. 7 .1 .2 Gaseous C ontam inants. Gaseous con taminants may be classified into two broad groups as follows: toxic and inert. The toxic or poisonous gases may produce harmful or objectionable response in man in relatively low concentrations, whereas the inert gases produce undesirable effects primarily by displacement of oxygen. The term "gases" as used here applies equally to gaseous substances (such as nitrogen, carbon monoxide, and carbon dioxide) and the vapors of volatile substances (such as benzene and carbon tetrachloride). The toxicity of gases and vapors for m an varies over a wide range. For instance, a 10-minute exposure to a concentration of 120 parts per million (ppm) of phosgene may be fatal, whereas one may safely Z2.1 28 AMERICAN STANDARD SAFETY CODE FOR breathe 1,000 ppm of dichlorodifluoro-methane (freon) throughout a working day. 7.1.2.1 Gaseous Contaminants Immediately Dangerous to Life, Gaseous contaminants immediately dangerous to life are gases present in concentrations that would endanger the life of a person breathing them for even a short period of time. For example, 400 to 500 parts of sulfur dioxide per million parts of air (0.04 to 0.05 percent) by volume is considered to be dangerous for a short exposure. 7.1.2.2 Gaseous Contaminants Not Immediately Dangerous to Life. Gaseous contaminants not im mediately dangerous to life are gases present in concentrations that could be breathed for a short period without endangering the life of a person breathing them, but which might produce discomfort and possible injury after a prolonged single exposure or repeated short exposures. For instance, the thresh old limit value for sulfur dioxide has been set at 5 ppm, based primarily on the irritating effect of this gas on the nose, eyes, and throat. 7.1.3 P articulate C ontam inants {D u sts, F um es, S m okes, Mists, F ogs). Particulate con taminants may be classified, according to their mode of action, into three broad groups as follows: (1) Toxic particulate contaminants that may pass from the lungs into the blood stream and are carried to the various parts of the body to exert their injurious effects. These effects may be chemical irritation, systemic poisoning, neoplasms (tumors), or such effects as hay fever, asthma, or simple febrile reac tions. (2) Fibrosis-producing dust, such as asbestos and free silica, or other pneumoconiosis-producing dusts that are not taken up by the blood stream but remain in the lungs and may cause significant pul monary impairment. (3) Nontoxic and nonfibrosisproducing particles (so-called nuisance dusts and mists) that may dissolve and pass directly into the blood stream or may remain in the lungs producing neither local nor systemic effects. Particulate contaminants may be classified accord ing to their physical properties into three broad groups as follows: (1) solid, such as dusts and fumes; (2) liquid, such as mists and fogs; and (3) a combination of solid and liquid, such as silicawater sprays and paint sprays. The majority of particulate contaminants are not immediately dangerous to life; that is, days, weeks, or even years of exposure may transpire before harmful effects are noted. Notable exceptions are dusts and mists containing the organic phosphorus insecticides which, if present in high concentrations, may incapacitate or even kill a man in a very short time. Other exceptions to this generalization are certain radioactive particulates and the toxic war smokes such as diphenylchloroarsine (DA) and diphenylaminechloroarsine (DM). 7,1.4 C om bination o f Gaseous and Parti culate C ontam inants. In addition to atmospheres containing gaseous or particulate contaminants, there are those in which both types occur simultaneously. The contaminants may be entirely different substances, such as carbon monoxide and oxides of nitrogen produced by blasting and the dust from the blasted material, or they may be the same substance in the liquid and in the vapor form, such as slightly volatile liquids that are atomized. The simultaneous occurence of both gaseous and particulate contaminants in an atmosphere complicates the procedure for providing adequate respiratory protection against them. 7.2 Classification of R espiratory Protective Devices. Respiratory protective devices fall into the following broad groupings on the basis of their mode of functioning: Atmosphere-supplying respirators Self-contained type Hose type Air-purifying respirators Gas masks or chemical cartridge respirators Self-rescue-type respirators Dispersoid (dust, fume, mist) respirators Combination gas and dispersoid respirators A more detailed classification, brief description, and the limitations of the various types of respir ators follow: 7.2.1 A tm o sp h ere-S u p p lyin g R espirators. Atmosphere-supplying respirators provide a respir able atmosphere to the wearer independent of his immediate atmospheric environment. They may be divided into two main subgroups: self-contained breathing apparatus and hose-type respirators. 7.2.1.1 Self-Contained Breathing Apparatus. A self-contained breathing apparatus is a respirator by means of which the user may obtain respirable air or oxygen from a supply of air, oxygen, or oxygen generating material which is an integral part of the respirator as worn. Self-contained breathing apparatus may be divided into two main subgroups: recirculat ing-type and demand-type. 7.2.1.1.1 Recirculating-Type Self-Contained Breathing Apparatus, Recirculating-type self-con tained breathing apparatus may furnish respirable oxygen to the wearer from either (1) a cylinder of Z2.1 HEAD, EYE, AND RESPIRATORY PROTECTION 29 rrot dio. irator| description/" *of xwpir;V ' ^ r ^ ^ r a . ' '- le^a.respirdent of his ey/may be df-con^ained 'j>parau\ A dqjiratorby i^ble'S ror . poiygen- compressed oxygen or (2) a canister containing an 7 ,2 iL L 3 Limitations of Self-Contained oxygen-generating m aterial, Breathing Apparatus. The self-contained breathing (1) Compressed Oxygen Type. The modaepopfaratus has no limitation as to the concentration functioning of the compressed-oxygen type is as follows: High-pressure oxygen from the cylinder passes through a pressure-reducing-and-regulating of gas or particulate matter or as to .a deficiency of oxygen in the atmosphere in which it is worn. How ever, many gases are very irritating to the skin and valve and an admission valve into a breathing bag to mucous membranes when present in high concen from which the wearer inhales through a corrugated trations; and hydrocyanic acid gas can be absorbed breathing tube connected to a mouthpiece or facepiece through a one-way check valve. The wearer's exhaled breath passes through another check valve in dangerous amounts through the unbroken skin. The wearer has complete freedom of movement, and may leave the work area through any available exit. and corrugated breathing tube to a container of chemical which removes the exhaled carbon dioxide. It then passes through a cooler and enters the breathing bag. In normal use, oxygen enters the breathing bag from the supply cylinder only when the volume of gas in the bag has decreased sufficiently to allow a pressure plate to act upon the admission valve which then admits oxygen until the wearer exhales. In the event that the pressure-reducing-andregulating valve or the admission valve does not function properly, oxygen may be admitted directly from the oxygen cylinder to the bag through a The length of time that he may remain in the irrespir able atmosphere is dependent upon the amount of oxygen or air made available to him by the apparatus and upon his activity. Self-contained breathing ap paratuses are rated according to whether they will protect for two hours, one hour, three quarters of an hour, or one-half hour while doing heavy work. If this type of respirator is to be used safely and with confidence, rather extensive training is required not only in its care and use but also in an understanding of its limitations. 7.2.1.2 Hose-Type Atmosphere-Supplying Res manually operated by-pass valve. Suitable pressure- pirators. Hose-type atmosphere-supplying respirators release and saliva traps are provided. make air available to the wearer through a hose connected to a supply of respirable air. They may be (2) Self-Generating Type. The mode of divided into four main subgroups: (1) hose mask functioning of the selfgenerating type is as follows: with blower, (2) hose mask without blower, (3) air Water vapor in the wearer's exhaled breath reacts line respirator, and (4) abrasive-blasting respirator, with the granular chemical fill of the canister to 7.2.1.2.1 Hose Mask with Blower. The hose liberate oxygen which then enters the breathing bag mask with blower (Type A supplied-air respirator) from which the wearer inhales through a corrugated consists of a full facepiece to which respirable air breathing tube connected to a facepiece. Check valves is forced through a large-diameter flexible hose by maintain a unidirectional flow of gases in the closed a hand or motor-operated blower, and through which system. The rate of evolution of oxygen is governed the wearer can inhale whether or not the blower is by the volume rate of breathing of the wearer. operated. Check valves allow air flow only toward Exhaled carbon dioxide is removed by the canister. the facepiece. The hose is attached to the wearer's A suitable manually operated pressure-relief valve body by means of a rugged safety harness which has is provided. provision for the attachment of a safety line; with this 7.2.1.1.2 D em an d -T y p e S e lf-C o n ta in ehdarness and line the wearer may be drawn to safety Breathing Apparatus. Demand-type self-contained in an emergency. Usually, the hose mask with blower apparatus is designed to supply air or oxygen to the wearer. These gases are not to be used interchange > ably; that is, oxygen should never be used in an apparatus designed for compressed air, and vice versa. is designed so that two facepiece-harness-and-hose assemblies may be attached to a single, double-outlet blower. 7.2.1.2.2 Limitations of Hose Mask With The mode of functioning of the demand-type self- Blower. The hose mask with blower (Type A supplied- contained breathing apparatus is as follows: Oxygen air respirator) has no limitations as to concentration or air is admitted to the facepiece from a cylinder of gas or particulate matter or a deficiency of oxygen of the compressed gas through a two-stage pressure- in the atmosphere in which it is worn. However, reducing mechanism only when the wearer inhales, many gases are very irritating to the skin and mucous and in quantities governed by his breathing. The membranes when present in high concentrations; and wearer's exhaled breath escapes to the surrounding hydrocyanic acid gas can be absorbed in dangerous atmosphere. amounts through the unbroken skin. The wearer is Z2.1 30 limited by tbe length of the air-supply hose to travel within 150 feet of the blower which must be in respirable air. He must return to fresh air by retrac ing his route in the contaminated atmosphere, other wise the air-supply hose would become entangled. It provides respiratory protection for an unlimited period. 7 .2 .1 .2 .3 Hose Mask Without Blower. The hose mask without blower (Type B supplied-air res pirator) consists of a full facepiece to which a supply of respirable air may be drawn through a large-diameter flexible hose by the wearer's breath ing effort. Check valves allow air flow only toward the facepiece. The hose is attached to the wearer's body by a suitable harness. The air-inlet end of the hose is provided with a fine-mesh screen to prevent entrance of coarse particulate matter and with a means of anchoring the inlet in respirable air. 7.2.1.2.4 Limitations of Hose Mask Without Blower. The hose mask without blower (Type B supplied-air respirator) is limited to use in any atmosphere from which the wearer can escape un harmed without the aid of the respirator. The wearer is limited by the length of the air-supply hose to travel within 75 feet of an assured source of respirable air in which the air-inlet end of the hose must be placed. It provides respiratory protection for an unlimited period. 7 .2 .1 .2 .5 Air-Line Respirator. Air-line res pirators (Type C supplied-air respirators) consist of a half-mask facepiece, full facepiece, or a loose-fitting helmet or hood to which respirable air is supplied through a small-diameter hose. They may be divided into two classes: (1) continuous-flow class and (2) demand class. 7 .2 .1 .2 .5 .1 Continuous-How Class AirLine Respirator. Continuous-flow class air-line res pirators (Type C and CE supplied-air respirators) supply a continuous flow of respirable air to the facepiece, helmet, or hood through a small-diameter hose. The wearer's exhaled air and the excess air entering the facepiece, helmet, or hood covering escapes to the surrounding atmosphere. Provision is made for attaching the air-supply hose to the wearer and for detaching the air-supply hose rapidly in an emergency. The respirator is designed to allow at least 4 cubic feet of air per minute to enter the facepiece and at least 6 cubic feet of air per minute to enter the helmet or hood. 7 .2 .1 .2 .5 .2 Abrasive-Blasting Respirator, The principle of operation of the abrasive-blasting respirator (Type CE supplied-air respirator) is the AMERICAN STANDARD SAFETY CODE FOR i \ same as that of the continuous-flow class air-line respirator. However, it is constructed so that it will protect the head and the neck of the wearer and the eyepiece of the respirator from the rebounding abrasive. The respirator is designed to allow at least 4 cubic feet of air per minute to enter the facepiece t and at least 6 cubic feet of air per minute to enter ; the helmet or hood. Only a full facepiece or hood and helmet is used with this respirator. 7.2.1.2.5.3 Demand-Class Air-Line Res pirator. Demand-class air-line respirators (Type C supplied-air respirators) supply respirable air to the facepiece only when the wearer inhales, and at a rate governed by his volume rate of breathing. A source of respirable air, either an air compressor or \ a container of compressed air, is attached by a small- diameter hose to a demand valve which is actuated jj by a slight negative pressure created when the wearer ^ inhales. Upon actuation, it allows air to flow to the \ facepiece through a flexible corrugated breathing tube. Upon exhalation, the demand valve closes and permits no air to flow to the respirator. The exhaled breath escapes to the surrounding atmosphere through an exhalation valve or valves. The demand valve is attached to the wearer ao as to allow the air-supply line to be dragged behind the wearer without exerting a pull on the facepiece. Provision is made for detach ing the air-supply hose rapidly in an emergency. Helmets or hoods are not used with this respirator. 7.2.1.2.6 Limitations of Air-Line Respira tors. The air-line respirator (Type C supplied-air respirator) and the abrasive-blasting respirator (Type CE supplied-air respirator) are limited to use in concentrations of gases or vapors that are not im mediately harmful or from which the wearer can escape unharmed without the aid of the respirator. They are not to be worn in an oxygen-deficient atmosphere. The wearer's travel is limited by the length of the air-supply hose, and he must retrace his route in the contaminated atmosphere to return to fresh air while wearing the respirator. These respirators shall be used within the limits set by the manufacturer for air-supply hose length and range of air pressure applied to the inlet of the air-supply hose. They provide respiratory protection for an unlimited period. 7 .2 .2 A ir-P u rifyin g R espirators. Air-purifying respirators remove gaseous or particulate contamin ants, or both, from otherwise respirable air that is inhaled by the wearer. They may be divided into three classes; (1) chem ical-filter type, (2) mechan- ical-filter type, and (3) combination chemical- and mechanical-filter type. ine! assai Z2.1 HEAD, EYE, AND RESPIRATORY PROTECTION 31 7.2.2.1 Chemical-Filter Respirators. Chemical- organic vapors, or a combination of two or more filter respirators such as gas masks, chemical-cartridge classes of gases or vapors such as acid gases and respirators (non-emergency gas respirators), and self organic vapors or all gases and vapors. The canisters rescue-type respirators remove toxic gases and vapors of many types of gas masks are manufactured in from inspired air by sorption, chemical reaction, or two sizes, namely, regular or "industrial size," and oxidation by the granular fill of the canister or the large or "supersize" canisters. Everthing else cartridge. The exhaled breath escapes to the surround being equal, the large canister provides a longer ing atmosphere. service time than the regular size between changes of canisters, but the limitations of both in regard to 7.2.2.1.1 Gas Masks. Gas masks consist of ma aximum concentration of gas against which they canister, containing the appropriate granular fill, a will protect are the same. In most cases, a canister full facepiece, and a body harness to hold the canister designed for a single gas or a single class of gases securely in place on the body of the wearer. The and vapors will afford respiratory protection for a inspired air is drawn through the canister and considerably longer period than will a canister of enters the facepiece in such a manner as to inhibit the same size designed for protection against a the accumulation of moisture on the eyepieces. A check valve prevents exhaled breath from entering the canister and allows it to be forced out through an exhalation valve in the facepiece to the surround ing atmosphere. The facepiece is held securely to the wearer's face by an elastic head harness. Universal gas masks have an indicator or timer which shows when the canister should be changed for protection against carbon monoxide. multiplicity of gases and vapors. Gas-mask canisters manufactured in the United States of America are marked in bold letters with the name of the atmospheric contaminants for which the canister is intended or with the words "UNI VERSAL GAS-MASK CANISTER" in capitals, as well as being given a distinctive color in accordance with the American Standard Safety Code for Iden tification of Gas-Mask Canisters, K13.I-1950. These Gas masks are designed to provide respiratory colors serve as an aid to rapid identification of protection against a single specific gas such as canisters. The table from 6.1 of the above code is chlorine, a single class of gases or vapors such as reproduced here for ready reference (see Table 4). Table 4 Color Code for Gas-Mask Canisters Canister, Type Letter A A A B C k D I AE, etc 1 AB 1 - ABC B* N Atmospheric Contaminants To Be Protected Against Acid gases Hydrocyanic acid gas Chlorine gas Organic vapors Ammonia gas Carbon monoxide Dust, fumes, mists, fogs, and smokes in combination with any of the above gases or vapors Acid gases and organic vapors Acid gases, organic vapors, and ammonia gas All of the above atmospheric contaminants Color Assigned1 White* White with 5/-inch green stripe around the canister near the botton White with %-inch yellow stripe around the canister near the bottom Black* Green Blue Vh-inch contrasting black or white stripe around the canister near the top Yellow Brown Red. Filters are included in this canister, but stripes to in d ic a te th e m a re u n n ecessary . Note 1 : Gray shall not be assigned as the color for any gas-mask canister. L N ote 2: Canisters for a single gas or vapor other than ammonia or carbon monoxide shall have a -Vi-inch colored stripe around [the canister near the bottom. i Z2.1 32 AMERICAN STANDARD SAFETY CODE FOR 7.2.2.1.2 Limitations of Gas Masks. gas mask is limited to use in atmospheres containing at least 16 percent of oxygen and not more than 2 percent of most toxic gases (3 percent of ammonia). Many gases are very irritating to the skin and to the mucous membranes when present in these maximum concentrations; and hydrocyanic acid gas can be absorbed in dangerous amounts through the unbroken skin, its effects depending mainly upon the concentration of the gas and the duration of the exposure. The wearer has complete freedom of movement. A gas mask provides respiratory protec* tion for a period that depends on the type of canister, the concentration of the gas, and the activity of the wearer. A gas mask with canister for protection against carbon monoxide should have an indicator to show when the canister is to be replaced. No practicable method is available to warn the wearer of leakage of relatively odorless gases through the canister. It is important that the proper gas-mask canister be used for the intended purpose. For instance, an ammonia gas-mask canister will not afford respiratory protection against acid gases, organic vapors, or carbon monoxide. 7.2.2.1.3 Chem ical-Cartridge Respirators. Chemical-cartridge respirators (non-emergency gas respirators) consist of a half-mask facepiece to which is attached one or two cartridges. Like canisters, the cartridges are filled with granular materials that remove gases or vapors from the air drawn through them. Check valves prevent exhaled breath from entering the cartridges and allow it to be forced out through an exhalation valve in the facepiece to the surrounding atmosphere. The facepiece is held secure ly to the wearer's face by elastic headbands. The cartridges are usually designed to provide respiratory protection against single gases or vapors or against single classes of gases and vapors. They are easily removed and replaced. 7 .2 .2 .1 .4 Limitations of Chemical-Cartridge Respirators. The chemical-cartridge respirator (non emergency gas respirator) is limited to use in atmospheres that are not immediately dangerous to life; hence, it shall not be worn in an atmosphere deficient in oxygen. The wearer has complete freedom of movement. A chemical-cartridge respirator provides respiratory protection for a period that depends on the type of cartridge used, the concentration of the gas or vapor, and the wearer's activity. Its use is limited to low concentrations of certain gases and vapors such as a maximum of 0.1 percent (1,000 ppm) of organic vapors. It should not be used for Thperotection against (1) harmful gases or vapors that cannot be detected by the sense of smell; (2) gases or vapors that are highly toxic in low concentration, 1 such as phosgene and arsine; or (3) concentrations : of gases and vapors that are highly irritating to th eyes. It is important that the proper chemical cartridge be used for the intended purpose; for instance, an organic vapor cartridge will not afford respiratory protection against ammonia. Knitted cotton covers for the face-contacting surface of the facepiece should not be used since they are not gastight. 7.2.2.1.5 Self-Rescue-Type Respirators. The self-rescue-type respirator is designed to provide the greatest possible respiratory protection consistent with the practicability of carrying the device at all times so that it is always available for use during escape in the event of a catastrophe. It consists essentially of a small filter element, a mouthpiece, a nose clip, and a means of carrying the device conveniently on the body or storing it near the work .8 location. Most filter elements are similar to chemical cartridges made for protection against specific gases or vapors, but particulate filters are also available. One self-rescue-type respirator offers protection against carbon monoxide present in the atmosphere following an explosion or fire in a mine. The filter cartridge for this type shall be protected from moisture to keep the chemical fill active. 7.2.2.1.6 Limitations of Self-Rescue-Type Respirators. Self-rescue-type respirators should never be used as a working tool, but only as a means dur ing escape from a contaminated area to enhance the possibility of reaching a safe atmosphere or a more positive type of respiratory protective equipment. The magnitude of protection afforded usually falls be tween that provided by gas masks and by chemical- cartridge respirators. For example, the self-rescue- type respirator for protection against carbon monox ide will provide at least 30 minutes service in an atmosphere containing 1 percent by volume of carbon monoxide. 7.2.2.2 Mechanical-Filter Respirators. Mechan ical-filter respirators such as dust, fume, or mist respirators remove particulate matter from the inspired air by capture on the filter, which is usually a fibrous pad. These respirators consist of a full or half-mask facepiece to which are attached one or two filters through which the inspired air is drawn. Check valves, present in most mechanical- filter respirators, prevent exhaled breath from passing through the filters and allow it to be forced out through an exhalation valve in the facepiece to the Z2.1 HEAD, EYE, AND RESPIRATORY PROTECTION 33 ah natanc respnal ttoncov uecesEl orovid It. COI uthpie the deraeS r the work o che.mAic` '* cific ga available^ protection | itmosphere| The ited from ! scue-Typftg ould never;! leans dur*| lhance theij or a more1! ment. The' falls be-* chemical-'' elf-rescue>n monoxice in an of carhon . Meehan. or mist from the is usually of a full ched one id air is ichanicalm passing ireed out ce to the iurrounding atmosphere. The facepiece is held se provide respiratory protection against particulate curely to the wearer's face by elastic headbands. matter, in addition to the respiratory protection .Knitted cotton covers are sometimes used to cover against gases and vapors furnished by their granular the face-contacting surface of the facepiece to absorb fill. Some chemical-cartridge respirators contain perspiration and to prevent irritation of the skin filters for the same purpose. Others have filters .when the respirator is worn in hot places or in air attached so that the filters may he changed one or containing certain irritating dusts such as lime. more times before the cartridges are changed. The Mechanical-filter respirators are designed to provide type of protection afforded by the filters in gas-mask respiratory protection against a single specific dust, canisters and chemical-cartridge-respirator cartridges :fume, or mist, a single class such as toxic dusts, or is stated on their labels. acombination of several classes of particulate matter 7.2.2.5 Limitations of Combination Chemical- such as dusts, fumes, and mists. and-Mechanical-Fliter Respirators. The limitations of The filters may be of the single-use or re-usable combination chemical-and-mechanical-filter respira type. Single-use filters cannot be cleaned and re-used, tors generally are the same as for each type of [but should be discarded after they have served their respirator given in the preceding sections. However, purpose. Re-usable filters, cleaned mechanically ac the limitation of dust filters in regard to protection cording to the manufacturer's instructions, may he against gases and vapors given in 7.2.2.3 obviously re-used. They should never be washed or treated with is modified by the type of protection afforded by solvents. the chemical-filter respirator (gas-mask or chemical- 7.2.2.3 Limitations of Mechanical-Filter Res cartridge respirator) against gases and vapors. pirators. There is a practical limit for the concentra tions in which a mechanical-filter respirator should be used. This is determined by the time required to plug the filter. For example, if the concentration is so high that the filter must he changed several times an hour in order that the wearer can inhale without undue resistance, a more suitable type of respiratory protective device should be selected. Mechanical-filter respirators should not be used in sand- or shot blasting operations in which one might he exposed to heavy concentrations of particulate matter and to rapidly rebounding particles of the abrasive. For 7.3 Requirements for Respirators. Respirators of all types should be capable of providing an adequate degree of respiratory protection against given atmospheric contaminants when the proper type has been chosen and when it is maintained and used correctly. Specific requirements for most of the types of respirators used in industry in the United States of America have been set up by the Federal Bureau of Mines. These requirements are published as Bureau of Mines Schedules, a list of which fol lows:2 such conditions, the abrasive-blasting respirator shall be used. Mechanical-filter respirators do not protect against gases and vapors or against an atmosphere deficient in oxygen. The wearer has complete freedom of Bureau of Mines, Procedure for Establishing a List of Permissible Self-Contained Mine Rescue Breathing Apparatus; Fees, Character of Tests, and Conditions Under Which Mine Rescue Breathing Apparatus Will Be Tested: Schedule 13, March 5, movement. The useful life of the filters is limited by the build-up of resistance to inhalation as the con 1919, 13 pp; Schedule 13A (revision of Schedule 13), January 21, 1930, 12 pp; Schedule 13B (re taminant is removed by the filter. The higher the vision of Schedule 13A), August 12, 1935, 12 pp; concentration of contaminant in the air drawn into Schedule 13C (revision of Schedule 13B), July 9, the filter and the greater the wearer's activity, the 1946, 11 pp; Schedule 13D (revision of Schedule more rapidly the resistance to inhalation increases. 13C), September 22, 1956, 12 pp. (Code of Federal This applies particularly to dusts and fumes. Hence, Regulations reference: 30 CFR Part 11.) the use of dust and fume respirators in high con Bureau of Mines, Procedure for Establishing a m centrations of these contaminants requires frequent List of Permissible Gas Masks; Fees, Character of replacement of disposable filters or frequent cleaning Tests, and Conditions Under Which Gas Masks Will i of re-usable filters. Be Tested: Schedule 14, May 22, 1919, 13 pp; 7.2.2.4 Combination Chemical-and-Mechanical- Supplement to Schedule 14, January 6, 1920, 4 pp; Filter Respirators. Combination chemical-and-mechanical-filter respirators remove toxic gases and vapors and particulate matter from inspired air. Some gas-mask canisters contain special filters which 2 Copies of the most recent Bureau of Mines Schedules and List of Respiratory Protective Devices Approved by the Bureau of Mines may be obtained from the Publications Distribution Section, Bureau of Mines, 4800 Forbes Street, Pittsburgh 13, Pennsylvania. 34 AMERICAN STANDARD SAFETY CODE FOR 3 5 Schedule 14A (revision of Schedule 14), August 25, 1923, 15 pp; Schedule 14B (revision of Schedule 14A), August 7,1930,13 pp; Schedule 14C (revision of Schedule 14B), August 20, 1934, 17 pp; Schedule 14D (revision of Schedule 14C), May 9,1935,17 pp; Schedule 14E (revision of Schedule 14D), December 24,1941,19 pp; Schedule 14F (revision of Schedule 14E), April 23, 1955. (Code of Federal Regulations reference: 30 CFR P art 13.) Bureau of Mines, Procedure for Testing Hose Masks for Permissibility: Schedule 19, April 28, 1927, 8 pp; Supplement to Schedule 19, August 20, 1934, 3 pp. Procedure for Testing Supplied-Air Respirators for Permissibility: Schedule 19A (re* vision of Schedule 19 and supplement, enlarged to include special hose masks without blowers, air-line respirators, and abrasive-blasting helmets, hoods, or masks), August 9, 1937, 21 pp; Schedule 19A as amended in the Federal Register on March 13, 1948, to include Type C, demand-class supplied-air res pirators; Schedule 19B (revision of Schedule 19A), April 19, 1955. (Code of Federal Regulations refer ence: 30 CFR Part 12.) Bureau of Mines, Procedure for Testing Filter-Type Dust, Fume, and Mist Respirators for Permissibility: Schedule 21, August 20, 1934, 14 pp; Schedule 21A (revision of Schedule 21), April 19, 1955. (Code of Federal Regulations reference: 30 CFR Part 14.) Bureau of Mines, Procedure for Testing Non emergency Gas Respirators (Chemical Cartridge Res pirators) for Permissibility: Schedule 23, November 13,1944,10 pp; Schedule 23A (revision of Schedule 23), April 23, 1955. (Code of Federal Regulations reference: 30 CFR Part 14A.) Each respirator that has been approved by the Bureau of Mines has met the requirements of the pertinent schedule that was in effect at the time of the approval. In general, each revision of a Bureau of Mines schedule makes these requirements more severe. A Bureau of Mines approval on a respirator remains in effect even though the schedule under which it was approved has been revised one or more times since then. Hence, if the user wishes to check on the minimum performance that he may expect from the respirator, he should consult the schedule or revision thereof, which is shown in the list of schedules as being in effect when the approval was granted. The Bureau of Mines performance requirements for a respirator are based on its field of use and upon three fundam ental requirem ents fo r a satisfac tory device: (1) It must provide adequate protection for a satisfactory period; (2) It must be reasonably comfortable and convenient to wear; and (3) It j must be constructed of durable materials. If no ! Bureau of Mines schedule applies to a respirator being considered for use, it should be examined to ; see that it fulfills these three requirements. Further judgment might be based on its compliance with the , performance requirements of the most closely related respirator approved by the Bureau of Mines. 7.4 Selection of R espirators 7.4.1 General Considerations. In choosing a respirator to be used for respiratory protection in any given situation, the following factors should a be considered: (1) the nature of the hazard; (2) ; the severity of the hazard; (3) the type of con- \ taminant; (4) the concentration of the contaminant; J (5) the period for which respiratory protection must 5 be afforded; (6) the location of the contaminated j area with respect to a source of respirable air; (7) | the expected activity of the wearer; and (8) the operating characteristics and limitations of the avail- ] able respirators. j Table 5 lists the hazards and the respirators that ' are designed specifically to afford respiratory protection against them. By reference to this table, and | by considering the foregoing factors, the user can 1] determine the type of respirator that should be j used. The self-contained breathing apparatus and the -j hose mask with blower would give respiratory protec- 1 tion against any of the hazards listed, but these \ devices are not included in the list of respirators j that could be used in the less hazardous situations 4 because their use would amount to "over-engineer- ' ing-" ! ? Even though most of the factors in 7.4.1 are 1' interrelated, a brief discussion of each follows: i 7 .4 .1 .1 Nature of the Hazard. The user should determine whether or not the atmosphere is deficient in oxygen, and whether the contaminant is gaseous j or particulate, or a combination of the two. 7.4.1.2 Severity of the Hazard. The user should determine whether or not the atmosphere is im mediately dangerous to life. This is discussed under Classification of Hazards in 7.1. 7 .4.1.3 Type of Contaminant 7.4.1.3.1 Gaseous Contaminant. Where the contaminant is gaseous, the user should determine whether it is an acid gas, an organic vapor, ammonia, carbon monoxide, or a mixture of two or more of these gaseous co n tam in an ts. T h is in fo rm atio n is essential to the choice of the proper gas mask or chemical-cartridge respirator because the different .-.a '/'Si CODE TOR f HEAD, ETE, AND RESPIRATORY PROTECTION Z325.I id (3) It gi ils. If n o /- |l respirator/;i|| amined,to.4||f s. Further :e with the ely related ines. . '% hoosing a ' itection in .,"-i >rs should tzard; (2) | f )e of con* ntaminant; ction must ntaminated. e air; (7)\Jfj d (8) the f the avail*. Table 5 Selection of Respiratory Protective Device Hazard Respirator Oxygen deficiency Self-contained breathing apparatus Hose mask with blower Caseous contaminant Immediately dangerous to life Self-contained breathing apparatus Hose mask with blower Gas mask Not immediately dangerous to life Air-line respirator Hose mask without blower Chemical-cartridge respirator Particulate contaminant Dust, mist, or fume respirator Air-line respirator Abrasive-blasting respirator Combination gaseous and particulated contaminant Immediately dangerous to life Self-contained breathing apparatus Hose mask with blower Cas mask with special filter Not immediately dangerous to life Air-line respirator Hose mask without blower Chemical-cartridge respirator with special filter rators that ory p ro te c -/| table, and, e user can si should be j tus and the jj :ory protecbut these .| respirators 3 situations er-engineer- M i 7.4.1 are llows: user should "! is deficient t is gaseous -; o. 'J user should here is im- ' ussed under types of gases require different absorbents or com dispersoid respirator may give an adequate degree binations of absorbents to remove them from the of protection, yet its service life may be too short inspired air. to be practicable or economical. That is, the filter 7.4.1.3.2 Particulate Contaminant. Wherme ay plug too readily with a rapid increase in the the contaminant is particulate, the user should know inhalation resistance, thus necessitating frequent its physical form; that is, whether it is a dust, fume, changing or cleaning of the filter material. Where or mist. Furthermore, he should know whether it practicable, an air-line respirator should be used in is a toxic type (containing, for instance, arsenic, anti high concentrations of particulate matter. mony, cadmium, or lead), a pneumoconiosis-produc 7.4.1.5 Period of Required Respiratory Protec ing type (containing, for instance, asbestos or free tion. The period of respiratory protection required silica), or a type having a low order of toxicity and has considerable bearing on the decision about which being nonfibrosis producing (containing, for in type of respirator to use in any given situation. The stance, flour or wood). This information is essential self-contained breathing apparatus, the gas mask, to the choice of the proper dispersoid respirator, and the chemical-cartridge respirator provide respira as a respirator designed to protect against one type tory protection for a limited period, whereas the of particulate matter does not necessarily afford hose mask with blower, the air-line respirator, and adequate protection or service life against the other the abrasive-blasting respirator do so for an unlimited types. period; thus, for protracted periods of use, the latter 7 .4 .1 .4 Concentration of Contaminant types offer some advantages. 7 .4 .1 .4 .1 Gaseous Contaminant. Where the 7 .4 .1 .6 Location of Contaminated Area with contaminant is gaseous, the maximum expected con Respect to Source of Respirable Air. This is a factor centration of the gas should be known. Where this that is frequently overlooked when choosing a respira Where the d determine > >r, ammonia, or more of ; ormation is ;as mask o r, the different : "J is above 3 percent by volume of ammonia gas, or 2 percent by volume of other gases, a gas mask is not adequate and should not be used. If it is above 0.1 percent by volume (1,000 ppm) of organic vapors, an organic-vapor chemical-cartridge respirator is not adequate and should not be used. 7 .4 .1 .4 .2 Particulate Contaminant. Where the contaminant is particulate, the proper type of tor. In using a hose mask, air-line respirator, or abrasive-blasting respirator, the distance that the wearer can go into a contaminated atmosphere is limited by the length of the hose connected to the source of respirable air. Furthermore, the presence of the hose requires that he enter and leave the area by the same route. When wearing a self-contained breath ing apparatus or a gas mask, a person may leave the ] Z2.1 36 AMERICAN STANDARD SAFETY. CODE FOR contaminated area by another exit, but he should 7 .5 .2 Precautions To Be Taken in the Use of make certain that the device will afford protection Respirators for a period adequate for him to reach fresh air, 7.5.2.1 Precautions To Be Taken in the Use of taking into account possible delays. For instance, a Self-Contained Breathing Apparatus in mine-rescue work, the maximum distance from (1) The wearer of a self-contained breathing fresh air that a crew wearing 2-hour self-contained apparatus should be physically sound and fit and breathing apparatus should cover is 1,000 feet (2,000 should be thoroughly trained in the construction, feet round trip) under ideal conditions. This distance testin g , use, care, and limitations of the apparatus is decreased to not more than 50 feet from fresh air before he attempts to wear such apparatus in a if the crew has to crawl in a low passage. hazardous situation. 7.4.1.7 Activity of the Wearer. In many in (2) Make certain that the self-contained stances, the respirator that would be first choice from breathing apparatus is in good operating condition. the standpoint of respiratory protection or period of (3) Make certain that the apparatus is capable protection cannot be used because it would limit of supplying air or oxygen for the period that the the activity of the wearer. For instance, a hose mask wearer must remain in the contaminated area. would not be practicable for use where the wearer (4) Adjust the apparatus to the wearer and s has to weave in and out of a series of obstructions test for tightness according to the manufacturer's such as pipes because of the difficulty of pulling the instructions. heavy hose after him and his inability to escape (5) If the wearer is to enter a confined space quickly to fresh air in event of danger. An air-line containing an atmosphere that is extremely hazardous, ] respirator would likewise be rather impracticable connect a strong life line to his body. This will serve ) for use where the wearer must be moving about (a) as a means of guiding him to the exit; (b) as ' constantly in the contaminated area, or going from a means of transmitting prearranged signals between one room to another, because of the inconvenience him and the men at the fresh-air base; and (c) as and tripping hazard of the air-supply hose. a means of aiding in rescue operations in case of an j The activity of the wearer has a marked effect on accident or emergency. This life line should be held the life to be expected from a self-contained breath by two attendants, at least one of whom is wearing i ing apparatus, gas mask, chemical-cartridge respira a similar apparatus. tor, or dispersoid respirator. The volume of air (6) Enter the contaminated area cautiously, breathed by a man walking at a rate of 4 miles per and, if the contaminant is detected by odor, taste, or - hour is more than three times that breathed when eye, nose, or throat irritation, return to fresh air he is standing still. Hence, the supply of oxygen immediately and ascertain the cause. 1 in a self-contained breathing apparatus is used up (7) Bear in mind the time limitations of the faster, the absorbent capacity of a gas-mask canister apparatus and allow an adequate margin of time or a chemical cartridge is exhausted faster, and the for the return to fresh air. filter of a dispersoid respirator would be plugged (8) The mouthpiece and nose clip, or the faster while the wearer is exercising than when he facepiece, should not be removed until the wearer is at rest. is certain that he is in respirable air. 7.4.1.8 Operating Characteristics and Limita tions of the Available Respirators. The operating 7.5.2.2 Precautions To Be Taken in the Use of characteristics and limitations of respirators have a Gas Mask been discussed in 7.2. (1) Make certain that the gas mask is in 7.5 Use and M aintenance of R espirators good operating condition. 7.5.1 General Considerations. Respirators are (2) Adjust the canister harness on the body used to supplement other methods of control of air so that, when the facepiece is put on, there is some borne contaminants rather than to substitute for slack in the breathing tube when the wearer's head them. Every effort should be made to prevent the is in the normal position. dissemination of contaminants into the breathing (3) Adjust the facepiece to make a gastight zones of the workers. In some instances, it is necessary fit on the wearer's face. There are two means of to use respirators only until these control measures testing a facepiece for a gastight fit: (a) Close off the have been taken; in others, such measures are im exhalation valve and exhale gently into the facepiece. practicable, and the continued use of respirators is If a slight positive pressure can be built up in the face- necessary. piece without any indication of outward leakage of Z2.1 HEAD, EYE, AND RESPIRATORY PROTECTION 37 air between the facepiece and the face, it is adjusted (3) Connect the proper length of hose (not properly, (b) Close off the breathing tube, inhale so over 150 feet) to the blower and to the facepiece, that the facepiece starts to collapse, and hold the making sure that all gaskets are in place and that breath for about ten seconds. If the facepiece stays the connections are tight. Where more than one TW . d breathing in its partially collapsed condition and no inward leakage of air is detected, it is adjusted properly. hose line is to be used, each should originate at the blower. and fit an d | onstruction,* (4) Test the complete gas mask for gastightness by closing off the air-intake at the bottom (4) Before entering a confined space such as a tank or sewer containing an atmosphere that is e apparatus! of the canister, either with the palm of the hand extremely hazardous, connect a strong life line to ira tu s-tM- --fya or with the bottom canister seal, and inhaling as in (3) (b) above. the D-ring of the body harness. This life line should be held by two attendants so that the wearer can Ifcontained! This test checks the gastightness of the canister be removed from the contaminated atmosphere in I condition. ,' or timer gaskets and of the connection between the case of accident or emergency. is is capable,; breathing tube and the canister or timer. (5) Operate the blower for a minute or two od that the ; (5) Make certain that the contaminated at at a rapid rate to blow any dust out of the hose and area. Ssr/i mosphere is not deficient in oxygen. to make sure that air is being delivered to the wearer and) (6) Enter the contaminated area cautiously. facepiece. nufacturer'sf If the odor of the contaminant is noted, return to (6) Adjust the body harness securely to the 1 fresh air immediately and ascertain the cause of wearer. lfined space) the leakage. (7) Adjust the facepiece to the wearer so that hazardous,! is will serve;! xit; (b) as-, als between| and (c) a s;| i case of an `; (7) Make certain that the canister has enough residual life to give respiratory protection for the period that the wearer expects to be in the con taminated area. It is good practice to attach a fresh canister to the mask before entering an extremely hazardous atmosphere, especially one containing a it makes a gastight fit with his face. There are two means of testing for a satisfactory facepiece fit: (a) Close off the exhalation valve and exhale gently into the facepiece. If a slight positive pressure can be built up in the facepiece without any indication of outward leakage of air between the facepiece and uld be held*! gas that has poor warning properties, such as methyl the face, it is adjusted properly, (b) Close off the is wearing bromide. breathing tube or tubes, inhale so that the facepiece cautiously,' ^r, taste, or o fresh air i; tions of the ,in of time' r lip, or the (8) The facepiece should not be removed or fresh canisters attached until the wearer is certain that he is in respirable air. (9) After leaving the contaminated area, re place the bottom seal on the canister to prevent deterioration of the canister contents. This is par ticularly important in the case of universal gas-mask canisters. starts to collapse, and hold the breath for about 10 seconds. If the facepiece stays in its partially collapsed conditions and no inward leakage of air is detected, it is adjusted properly. (8) Operate the blower, and adjust the flow of air to the wearer's satisfaction. The blower should be operated continuously during the use of the mask. (9) Check on the prearranged signals be tween the wearer and the blower operator. the wearer J (10) Where the contaminant is a single gas (10) Enter the contaminated area cautiously. or vapor, or a mixture of two or more gases or (11) Be careful that the hose is not en the Use of j vapors of the same type, longer service time will be obtained if a canister is used that is designed dangered by sharp edges or falling objects, and re member that the wearer must retrace his steps and mask is in n the body- especially for protection against the contaminant than would be obtained if a universal gas-mask canister were used. Firemen generally use the universal gas mask canister because they are never certain what leave by the same route that he entered. (12) If the continuous flow of air to the facepiece is interrupted, the wearer should return to fresh air and ascertain the cause. ere is some gases they might encounter. (13) The facepiece should not be removed arer's head i a gastight until the wearer is certain that he is in respirable air. 7.5.2.3 Precautions To Be Taken in the Use of 7.5.2.4 Precautions To Be Taken in the Use a Hose Mask With Blower of a Hose Mask Without Blower > means of 5' (1) Make certain that the hose mask is in lose off the good operating condition. (1) Make certain that the hose mask is in good operating condition. e facepiece. ' (2) Set the blower in an assured source of (2) Securely fasten the air-intake of the in the face- ) respirable air. respirator in an assured source of respirable air. leakage of 1 Z2.1 38 AMERICAN STANDARD SAFETY CODE FOR ' 1 (3) Connect the proper length of hose (not the wearer according to the manufacturer's instruc over 75 feet) to the air-intake and to the face- tions. A full facepiece or half-mask facepiece should ' piece, making sure that all gaskets are in place and be adjusted so that all the excess air leaves the that the connections are tight. facepiece through the exhalation valve and none (4) Adjust the body harness to the wearer. is felt leaking out under the edge of the facepiece. (5) Adjust the facepiece to the wearer so (6) When the rate of flow of air into the that it makes a gastight fit with his face. facepiece, helmet, or hood seems to be excessive, the There are two means of testing for a satisfactory wearer may decrease the flow of air by means of facepiece fit: (a) Close off the exhalation valve and the air-regulating valve with which most air-line exhale gently into the facepiece. If a slight positive respirators are equipped. However, to prevent the pressure can be built up in the facepiece without contaminant in the surrounding air from reaching , any indication of outward leakage of air between the wearer's breathing zone, the flow of air should the facepiece and the face, it is adjusted properly, not be decreased below 4 cubic feet per minute for < (b) Close off the breathing tube, inhale so that facepieces, or below 6 cubic feet per minute for i the facepiece starts to collapse, and hold the breath helmets or hoods. Hence, the air-regulating valve for about 10 seconds. If the facepiece stays in its should be used judiciously on an air-line respirator. partially collapsed condition and no inward leakage (7) Enter the contaminated area cautiously i of air is detected, it is adjusted properly and is and leave by the same route. gastight. (8) Each air-line respirator is equipped with s (6) Make certain that the atmosphere to be a quick-acting detachable coupling by means of ' entered is not so hazardous that the wearer cannot which the wearer can quickly disconnect the respira- ] escape unharmed without the aid of the respirator. tor from the air-supply line to facilitate escape in . (7) Enter the contaminated area cautiously an emergency such as fire. The wearer should practice and leave by the same route. using this coupling before wearing the respirator i 7.5.2.5 Precautions To Be Taken in the Use of in a contaminated atmosphere. 4 an Air-Line Respirator 7.5.2.6 Precautions To Be Taken in the Use of (1) Make certain that the air supply is respir able. Close attention should be paid to the location of the intake to the air-supply device to make certain that the entering air is not contaminated. A suitable an Abrasive-Blasting Respirator. The precautions to J | be taken in the use of an abrasive-blasting respirator are the same as those given for the air-line respirator, 'M with the following additional precautions. a filter should be provided to remove objectionable (1) Make certain that the shatterproof eye- - 1 odors, oil and water mist, and rust particles from piece and the protective cover glass (if furnished) -1 the air delivered to the air-supply line. A suitable are in place. Under no circumstances should regular 1 reducing-type or demand-type valve and an excess- window glass be used in place of the shatterproof 1 pressure relief valve should also be provided. For eyepiece. Clean the inner and outer surfaces of all * supplying respirable air, the use of low-pressure eyepieces. externally lubricated blowers is preferable to high- (2) Make certain that the protective wire pressure internally lubricated compressors, since the screen or perforated-metal eyepiece is clean and in i latter may add objectionable odors to the air and place. may produce carbon monoxide upon overheating. Internally lubricated compressors should be equipped with an automatic shut-off which is actuated if they become overheated. (2) Make certain that the air-line respirator is in good operating condition. (3) Attach the proper length of air-supply hose to the source of compressed air and to the breathing tube. 7.5.2.7 Precautions To Be Taken in the Use of a Chemical-Cartridge Respirator (1) Make certain that the atmosphere to be entered is not dangerous to life. I (2) Make certain that the respirator is in good operating condition, that the gaskets are in place, and that the proper chemical cartridges are securely mounted in the respirator. (3) Adjust the respirator to the wearer's face (4) Adjust the pressure of the air at the inlet to. the air-supply hose so that it is within the proper so that it makes a gastight fit with his face. There : are two means of testing for a gastight fit: (a) Close pressure range. off the exhalation valve and exhale gently into the (5) Adjust the facepiece, helmet, or hood to facepiece. If a slight positive pressure can be built HEAD, EYE, AND RESPIRATORY PROTECTION l up in the facepiece without any indication of outward ] leakage of air between the facepiece and the face, it is 1 adjusted properly, (b) Close off the inlets to the face| piece by cardboard discs or stoppers usually furnished by the manufacturer, inhale so that the facepiece starts to collapse, and hold the breath for about 10 seconds. If the facepiece remains in its partially collapsed -! condition and no inward leakage of air is detected, it is adjusted properly. If the second method is used, the cardboard discs or stoppers must be re moved and the cartridges assembled with the face< piece without disturbing the fit of the facepiece on : the wearer's face. i (4) Enter the contaminated area cautiously. (5) When leakage of the contaminant is noted by the wearer, he should discard the used cartridges and replace them with fresh ones. 1 (6) Knitted cotton cloth must never be used 2 to cover the face-contacting edges of chemical-car- ;i tridge respirators, since the cloth cover is not gas- 3 tight. 7 .5 .2 .8 Precautions To Be Taken in the Use of 1a Dispersoid (Dust, Mist, or Fume) Respirator (1) Make certain that the respirator is in good operating condition and that the proper filters are securely fastened in place. (2) Adjust the respirator to the wearer's face so that it makes a dust-tight fit with his face. There are two means of testing for a satisfactory facepiece fit: (a) Close off the exhalation valve and exhale gently into the facepiece. If a slight | positive pressure can be built up in the facepiece * without any indication of outward leakage of air \ between the facepiece and the face, it is adjusted properly, (b) Close off the inlets to the facepiece > by cardboard discs or stoppers usually furnished ,,j by the manufacturer, inhale so that the facepiece ) starts to collapse, and hold the breath for about 10 i seconds. If the facepiece remains in its partially | collapsed condition, and no inward leakage of air is detected, it is adjusted properly. If the second | method is used, the cardboard discs or stoppers must :j be removed and the filters assembled with the face:) piece without disturbing the fit of the facepiece on ) the wearer's face. (3) As the total amount of solid particulate matter removed from the inspired air by the filter increases, the resistance to inhalation increases and Z2.1 39 filters should be cleaned in accordance with the manufacturer's instruction. Under no circumstances should respirator filters be washed or dry cleaned. (4) In atmospheres containing particulate matter that is irritating to the skin, or where excessive perspiration may occur, a knitted cotton cloth, furnished by the manufacturer, may be used over the edge of the facepiece to prevent contact between the rubber portion of the facepiece and the wearer's face. This must not be used on fume respirators. (5) When the facepiece is removed, the wearer may obtain visual evidence of the dusttightness of the facepiece fit by looking at his re flection in a m irror and noting the presence or absence of dust streaks on that portion of his face that was covered by the facepiece. 7.5.3 Instruction in Use of Respirators 7.5.3.1 General Considerations. For the safe use of any device, it is essential that the user be properly instructed in its selection, use, and mainten ance. This is particularly important with respect to respirators. Competent persons should give such instruction to the supervisors of all groups who may be required to wear respirators at their work. The supervisors, in turn, should instruct their men. No person should be allowed to wear a respirator of any type until he has received such instruction. Such instruction should cover: (1) An explanation of the need for using the respirator (2) Its operating principle (3) Steps to be taken to assure that it is in good operating condition (4) Proper adjustment of the respirator to the wearer (5) Proper use and maintenance of the res pirator The very presence of self-contained breathing apparatus, hose masks with blowers, or gas masks on the property of any organization is an indication that they are expected to be used in an emergency situation or in one that is dangerous to life. All persons who may have occasion to use these respira tors, or cause them to be used, should be properly trained in their use before circumstances require that they use them to protect their lives and the property of their employer. In addition to this, efforts should be made to foresee possible emergencies and plans of action should be formulated so that w hen resp ir atory protection is needed, rescue or repair operations will proceed smoothly and safely. Merely talking about such respirators as the self- Z2.1 40 AMERICAN STANDARD SAFETY CODE FQR i l f f i 1 ] contained breathing apparatus, the hose mask with blower, and the gas mask is not enough. The men should be given an opportunity to handle the respira tor, have it fitted to them properly, test the guslighlness of the facepiece fit, wear it in normal air for a period long enough for them to become familiar with it, and, finally, they should actually wear it in an irrespirable atmosphere. Such an atmosphere may be created by burning a half-ounce formaldehyde candle in a room of about 4,000 cubic foot capacity. Not only would this atmosphere be irrespirable, but it would be irritating to the eyes. This atmosphere is similar to that used by the Bureau of Mines in the training of men in the use of the self-contained breathing apparatus. After a person has worn one of these devices for a prolonged period in this formaldehyde-air mixture without any ill effect, he need only remove the facepiece or nose clip moment arily to be convinced of the efficacy of the respirator. Such training breeds confidence in the trainees that should stand them in good stead in an emergency situation.- A less severe training atmosphere that can be built up in any room without damage to its contents, or to other people in the same building, may be prepared by vaporizing isoamyl acetate to the amount of 173 cubic centimeters per 1,000 cubic foot capacity of the room. The liquid isoamyl acetate is vaporized from a cloth wick placed in front of a fan in the room. This produces a concentration of about 1,000 parts of isoamyl acetate per million parts of air (0.1 percent) by volume. If the odor of isoamyl acetate is detected by a person wearing an emergencytype respirator, he would be able to detect the odor of phosgene or chlorine if he entered a 2-percent concentration of either of these gases while wearing the device. Isoamyl acetate vapor in this concentra tion is used by the Bureau of Mines as a preliminary means of testing the gastightness of gas-mask facepieces before actually wearing them in highly toxic concentrations of gases. should be equipped adequately and manned .b y fjS y j trained personnel. .iK I B i 7.5.4.2 Procedures Applicable to All Respira* |1 tors 1 7.5.4.2.1 Inspection. All respirators should jj be inspected at regular intervals to make sure that J S they are ready for use. For respirators that are : 3 j used and maintained daily, inspection becomes a J | rather automatic function; however, it is often j | neglected for respirators that are stored throughout a plant for use in emergency situations. These devices ',! should be checked as regularly as fire extinguishersj as a matter of fact, it is good practice to integrate these inspection and maintenance programs. - -m All rubber parts such as facepieces, mouthpieces, ,19 exhalation valves, breathing tubes, and headbands1 I I should he inspected carefully for signs of deterioration ;,m such as hardening, checking, or tackiness. During the inspection, time should be given to "working" 3 the rubber between the fingers with a stretching and | j massaging action. This will reveal defects in rubber -- j l parts and prolong the life of non-defective parts. M A check should be made to see that all gaskets ,jm are present and that they are held in place tightly,' Metal parts should be checked for signs of cor* f s rosion, and plastic and glass parts for breakage. JB 7.5.4.2.2 Maintenance. When it is necessary to replace worn or deteriorated parts, only those JjS made specifically for the device should be used and the repair work should be accomplished by experi- enced personnel. Makeshift repairs for respiratory protective equipment cannot be tolerated. After m equipment that is used frequently is cleaned and |1 disinfected, it should be repaired routinely; emer- -I gency equipment should be repaired immediately j after inspection reveals the need for repairs. Repairs to intricate parts should not be attempted unless adequate facilities and trained personnel are available. For most users, it is preferable that parts of this type be replaced as a unit or returned to the manufacturer for repair. 7.5.4 Maintaining, Cleaning, Disinfecting, 7.5.4.2.3 Cleaning and Disinfecting. Respir and Storing Respirators atory protective equipment should be cleaned and 7.5.4.1 General Considerations. It is especially disinfected after each use. However, because of the important that respirators be properly maintained wide variety of materials used in these devices, the ! and stored. The life of the wearer may be dependent manufacturer should be consulted for the cleaning * on their proper functioning and ready availability. and disinfecting method best suited to his products. Adequate attention to cleaning and disinfecting is In general, facepieces and mouthpieces for respir also required because the respiratory inlet coverings atory protective devices are made from rubber or are worn on the face. Whenever possible, a centralized rubber-like compounds. Usually, these can be cleaned maintenance, cleaning, and storage station should be with detergent and lukewarm water by hand -b ru sh in g established to care for equipment of this type. It or agitation in a washing machine. Formaldehyde, j Z2.1 HEAD, EYE, AND RESPIRATORY PROTECTION 41 Oi NR ie' leaned.1.and >ely;, emermmediately airs. "**81 attemp':.-t-AS rsonneLj t (that parj med toth ? ng. Respire: leaned ndfj iuse ol the-, levices, ths ie cleaning products. , for respir-. rubber or' be cleaned id-brushing maldebyde, mdified phenolics, hypochlorite, or quaternary am replaced after use and that the oxygen cylinder is re monium compounds in the proper strength can be filled to rated capacity in order to insure full service ped to disinfect the parts. Normally all detergent is life. The cylinder pressure should be checked peri .rinsed from the protective device before disinfecting; odically and brought to rated pressure if necessary. owever, there are several combination cleaning and The tightness of the high pressure and low pressure 'disinfecting materials available id both liquid and sides of the apparatus should be checked periodically powder form which contain a detergent and quater following the manufacturer's instructions. In self nary ammonium salts and this permits combining the generating apparatus, periodic tightness tests as out ashing and disinfecting operations. After cleaning lined by the manufacturer should be followed. and disinfecting, the parts should be rinsed in clean 7 .5 .4 .3 .2 Hose Masks. Check the blower pe ater and dried quickly for most disinfectants. It may riodically for proper operation. Check hose for wear fiot be desirable to rinse parts treated with quaternary and tear after each use and steam clean when neces ammonium compounds since their disinfectant prop sary. Keeping hose capped when not in use will pre erties will continue indefinitely and may not produce vent entrance of dust or other contaminants. a skin irritation. After reassembly, the device should 7 .5 .4 .3 .3 Air-Line Respirators. The face- [be placed in a clean and dust-tight container. piece should he serviced after each use just as for all Hot waiter, steam, solvents, and ultraviolet light other respiratory protective equipment. The flow- should be avoided in the cleaning and disinfecting of control valves should be inspected after each use and rubber parts because all have deteriorating effects. If cleaned and repaired if necessary. Chemical car paint or other difficult-to-remove substances are en tridges in the continuous-flow control-valve assemblies countered, it is preferable that they be removed by should be changed when necessary. Air-line hose .mild caustic cleaners rather than by solvents. should be checked for wear and tear after each use 7.5.4.2.4 Storage. All types of respiratorasnd be steam cleaned when necessary. should be stored in clean and dry compartments under The air-supply system should be inspected routinely conditions of moderate temperature. Most devices of to insure continued proper functioning. Air compres this type are received in re-usable cartons or cases and sors, air-cylinder manifold systems, pressure reducers, should be kept in these containers during the period pressure-release valves, air-line filters, air-line instru of storage. Exposure to heat, sunlight, extreme cold, mentation, and permanent piping and outlet fittings and excessive moisture is harmful to respiratory pro must he kept in good repair to assure satisfactory tective devices if the exposure continues over ex condition of the air reaching the breathing zone of the tended periods. wearer. In some cases, it is necessary to locate respiratory protective devices at convenient stations throughout the work area for ready availability in the event of an emergency. Special care must be taken to insure ade quate storage under these conditions. In some in stances, it is necessary to construct special compart ments to protect the equipment from the process mate rials as well as from the elements. Additional emergency-type respiratory protective devices should be stored just outside the immediate danger area so that men can retreat to them and don them for judicious re-entry into the contaminated area to carry out rescue or repair operations. No respirator can be adequately stored outside its carrying case or carton in a tool box or clothing locker. 7 .5 .4 .3 .4 Gas masks. Check the facepiece to be sure that (1) the eyepieces are not broken and that they are held firmly in place; (2) the rubber portion of the facepiece is flexible and free from cracks; (3) the head harness is flexible and that the straps and buckles are in good condition; (4) the exhalation valve is in place, works freely, and has no dirt on its contact surfaces; (5) the breathing tube is flexible and free from cuts and that it is securely fastened to the canister neck or to the outlet of the timer; (6) the canister is of the proper type, is free from dents and rust spots, and is securely attached to the canister harness. If a timer is used, check to he sure that the gaskets are in place and are making proper contact, and that the timer is reset when a new canister is attached. Universal gas-mask canisters should be replaced after one year from date of break 7.5.4.3 Special Procedures for Maintaining, ing seal if not exhausted before this time. Canisters Cleaning, Disinfecting, and Storing Respirators sh o u ld h e sto re d 5n ft co o l, cle a n , d ry location and the 7 .5 .4 .3 .1 Self-Contained Breathing Apparastock rotated so that no canister remains in storage tus. In compressed-oxygen recirculating apparatus, for more than four years before it is used. make sure the carbon dioxide removing chemical is 7 .5 .4 .3 .5 Self-Rescuers. Frequent inspection Z2. 42 is the most important p h ase of th e m a in te n a n c e pro Some respirators employ re-cleanable filters, in gram with this type of equipment because the equip which case the filters are cleaned when the respirator ment is seldom used but must always be ready. The is being serviced. type which offers protection against carbon monoxide Chemical cartridges should be changed when the ; utilizes hopcalite in the chemical fill and must be pro wearer detects the odor or irritating effect of the con- j tected from moisture to remain effective. Follow the taminant. In plants with centralized maintenance sta manufacturer's recommendations for checking the tions, cartridges are sometimes discarded after a moisture seal at regular and frequent intervals. given period of use (based on group experience), but in most cases the wearer is responsible for discarding 1 7.5.4.3.6 Dispersoid and Chemical-Cartridgaend replacing cartridges in his respirator. Respirators. Mechanical filters of the "throw-away" Particular care should be exercised in the storage type should be discarded when the breathing resist of chemical cartridges because they usually deteri ance becomes bothersome to the wearer. In most orate if exposed to excess moisture and to gaseous air plants with centralized maintenance stations, the fil contaminants. Cartridges should not be stored in the j ters are destroyed and discarded at the time the area where it is necessary for the workmen to use respirator is serviced. chemical-cartridge respirators. 1