Document B8zv6komMpEOOBbDJj6GL261w

Dust, Fumes, Gases and Vapors WEDNESDAY MORNING SESSION October 28, 1942 Presiding:--Stuasx F. Meek, MD, Asst Medical Dir, Chrysler- Corp, Detroit Maintenance ol Exhaust Systems An Important Safety Measure ' By JOHN 1L KANE Engineer, American Air Filter Company, Inc, Louisville^ Kentucky In. recent years die safety, engineer's re in quickly setting up a routine check on the sponsibilities have! increased by leaps and performance of an exhaust system and catch bounds. Under hiswidening control logically ing any reduction in the system's effectiveness. comes the checking of exhaust systems for Tim. tods required under most cases are a die control of hazardous dusts and fumes. manometer (U-Gage), and a short piece of This discussion will assume that such haz ards are evaluated fay the industrial hygienist or safety engineer. Where exhaust ventila rubber tubing. The engineer must also have an understanding of static pressure losses and hood suction. tion is required, die ventilation engineer While hood suction readings have rightfully makes recommendations for exhaust capaci fallen into a state of ill repute'as a means of ties, system and hood design to control the measuring air flow, they do offera quick and condition. It will be further assumed that accurate method of measuring relative air this coordination results in an effective ex flow. If die hood suction is knbwn while an haust system removing the dust or fumes at exhaust system is functioning properly, its the points of generation and preventing their continued effectiveness can be assured as long dispersion to the workroom. Consequently, as toe hood suction does not reduce from its unless the process is changed, the hoods or original value. An expansion of this state enclosures altered, or the method of material ment should indicate why this simple mea handling revised, die'hazard should remain surement can be used as a ready check. controlled asJong as the exhaust system func tions property. The u^ord "properly" can .. The Exhaust System rigfctly be underscored because in many cases little attention is given to such an installation after toe project has been completed. Yet mechanical exhaust equipment and dust col lectors require die same attention that ma chine tool and. other plant equipment require and usually receive. Exhaust ventilation is by far toe most pre dominant means of controlling^ dust hazards. The fundamental dements and die design are not altered, wbetbcr tbe purpose of the ex haust system is to remove toxic or explosive particles, or simply to prevent dispersion for reduction-in workman fatigue^ improvement If- this ptecept is correct, a discussion of of visibility or general betterment of work- fundamentals may assist the safety engineer - ing conditions. In most cases die system will 55 56 31st National Safety Congress indude hoods or enclosures that surround and not a function.ef die hood suction except ' dust producing areas as completely as pos that velocities in die branch must be suffiddit able and as dose to die source oi dost gener . to convey die. material without adding and ation as'feasible and branch ducts that are .obstructing the: air flow by such accumula connected to the hood so an indraft of air can tions). be maintained through die necessary hood An analogy and some illustrations may help openings--thevdoaty of the incoming air to clarify this fundamental concept of exhaust sufficiently high to prevent material- flying- system design: outward. These velocities vary from 50 to 100 fpm forfumes and fine dusts, to 200Qjpm for large parddes forcefully thrown toward openings in die endosure. An aatomofate. requires more gas to accel erate from rest to 40 miles an hour than it does to travel.the same distance.at 40 miles per hour. Modi pf the power has. been used The sire of the duct connection is deter to overcome inertia and give die auto a ve- mined by die cubic feet of air to be exhausted Iodty pressure' (energynot used in overcom and the velocity necessary to prevent settling ing friction but available to coast after die in die ducts. Such velocities vary from-1000 engine Is stopped or to be expended by brak fpm for fumes to 5000 fpm for heavy loads of ing if the car fc stopped sooner); Similar coarse material. energy is required to move air from relative rest in a workroom to the spedfied velocities Note that velocities have been gaged by in an (exhaust duct An automobile requires smallness of particles and method of genera Ids gas' to accomplish tins acceleration on a tion. Dust and fume partidesare too small smooth hard surfaced road don on a rough and have too great surface area to be in fluenced greatly by the specific gravity of die material. The same velocities are generally used to confine or convey the tame size par. tide of wood or steel. gravd or dirt road. *"I\ In like manner less energy (entrance loss) is required to move air tbrou^t a flared hood which gradually changes its shape than/ through a hood with abrupt changes in shap^ An exhauster is the usual air moving equip ment that maintains the flow of air through hood and branches. It must have sufficient capodty to maintain the indraft at the hoods, and develop enough pressure to move dot or direction of air travel. ..... . The actuaT static pressure reading (the hood suction) ton vary widely dependent on die branch pipe velocities and hood entrance volume, overcoming die resistance to flow- of - loss. However,"ooce die hood design has been air from inertia, turbulence, doct resistance and collector loss; A dust collector removes the entrained material from die exhaust sys tem, concentrating die material for disposal, established and die branch pipe determined, anychange from the original hood suction can only indicate a change m velocity in the branch and consequently a. change Is air and preventing its re-entry to the workroom. volume removed from the hood. This relation will be true unless bood design has. been Definition of Hood Suction changed which would effect the cue . of ex hausting die air volume (entrance- loss), or obstructions or accumulations in hood.or In a branch duct dose to the hood, a static branch ahead of die point of hood suction pressure reading--!s called the hood suction. reading: Restriction of die cross sectional It is a measure of die pressure required to area will reduce the air volume, although induce air flow at the required velocity in die hood suction may even increase: dependent branch (velocity pressure) plus die pressure on location and degree of accumulation. .. lost in overcoming the resistance to air flow offered by die hood (entrance or acceleration loss). Measurement of Hood Suction y . .. , Hood suction therefore is a function of the Atthe tune of exhaust system installation, velocity of die air in the branch duct and the a A" hole; should .be drilled in each branch ease of getting that volume of air into die. connection for.static pressure (hood suction) duct (Effective dust control however, is a readings. Tim bote should be perpendicular function of the indraft vdocity at die hood to the duct: hi a straight section (4 to 6.dtam- il 9 Dust, Fumes, Gases and Vapors' 51 eters'loug if possible) at least one diameter from bood dr connecting elbow. Sudi small holds vrill.be'jii addition to larger pitot tube holm lor. actual measurement f air flow. ' FPM = feet per minute'Suriiig test FPMk = FPM.^ A vertical U-Gage is satisfactory for static . From toe above equations, it is possible to pressure readings above 18". Use an indined approximate toe actual volume of. air exhaust desigrt/for^lowar values. Both designs are ed through a branchductfromthehood suc The vertical type can be made tion reading. Such approximations'necessitate wi^a'Scale .divided into tenths of an inch estimation of die entrance loss of the hood. and * bent glass tube approximately in Unless such estimates are based on consider side,diameter mounted on asupport able experience they are 'subject to appred- The gage is leveled and zeroed and the length of rnbber hose attached to the proper side (either sidof the conventional U-Gage). able error. Consequently, a pitot tube should be used for determination of original air vol umes and the^use of hood suction readings restricted to checking for change, in exhaust Beading consists of measuring the distance volumes. in inches between the-top of toe water col umns in both legs of die U-Gage. Most man ufactured gages use a special gage oQ with scales calibrated .for the specific gravity and with toe reading indicated on only one leg of die gage. Be cerfain that toe and of die rubber tubing is held tightly over the Hbje in the duct while the reading is takeril Folding over the end of the rubber hose assures a tighter fit Check tubing for kinks or sharp \that would dose the passage. The pitot tube which measures the velocity of air flow in toe duct can, of course, be used for routine check purpbses instead, of the static pressure method described -above. In either case an understanding of hood suction is essential. The. hood' suction method of checking can more readily be delegated to an assistant ..without' technical training than the pitot tube where-care must be exercised in reading velocity pressures in the correct lo cation with the tube paralleling-the flow, of rily obtained static-pressure reading not'Ufly furnishes ah accurate check on.per formance, but the amount of change can be air. U-gages have been standard plant equip ment long enough to eliminate any feeling of uncertainty in its use. quickly calculated. It has been -previously As pre^ssure.- readings vary _as toe sho^ toat hood suction is a static pressm^f^ to "5! Jhange is magnified by comparison of gage biandi^ plus toe entrance ItMs wmch can >.be^ ^viioe5.' Normally/a reduction of volume or stated in terms of percentage of velocity pres- sure. Velocity pressure; entrance-l&s and most pressure losses vary as tbe square of the velocity of air flow. / velocity of 10 to' 15% will not be sufficient to reduce the effectiveness, of .die exhaust system. This, range is the.eqtrivalent to a reduction in static'pressure readings of 21 if. CFM -- cubic feet of air per minute ' to 32%. originally exhausted CFM* zs cubic feet of air per minute ex Causes for Reductio n in Hood Suction hausted during test A marked reduction in hood suction can often be traced-to one or more of the follow SP. l^ood suction originally noted. ing hems': reduced performance, by the ex - SP* =t hood suction daring test haust fan caused by reduced,speed due. to belt slippage, wear mi rotor or caring, or accumu CFM* = CFmA/SL lation in rotor or casing that would obstruct v SP.. air flow; or in tains of. conveying velocities in the branches-^ r ' tfl' FPM. =z'feet per minute originally main- tained Reduced performance caused by defects in the exhaust piping such as accumulations in branch or main ducts duel to insufficient-con veying velocities, condensation of oil or water vapors on duct walls, adhesive characteristics :<-j> .- ; . .;; mp: ilf; i]$ i 'fii- 58 31st National Safety Congress of material exhausted, or leakage losses caused by loose cleanout doors, broken joints, holes .worn in duct (mo$t frequent in elbows), poor connection to exhauster inlet Losses in suction can also be charged to additional exhaust points added to the sys tem (sometimes systems are designed for future connections and more air than re quired is handled by present brandies until future connections are made), change of set ting qf blast gates in branch lines (blast gates -adjust the air .distribution between the va rious branches. Tampering with Hast gates can seriously affect such distribution and therefore gates shonld be locked in place im mediately after.system has been installed and its effectiveness choked). Increased pres sure loss through dust collector due to lack of maintenance, improper operation, wear, etc. vary with tiie collector design. Refer to op* eration and maintenance instructions fur nished with the collector or consult the equipment manufacturer. |3IP h j .. Testing Toxic Atmospheres By N. R. BERN2 Chief Industrial Hygienist, The Fidelity ft Casualty Co. of N.Y, New York, New York In manufacturing, many operations and processes of one industry are common to those of another, although the two indus tries may be engaged in the production of entirely different types of goods. For example, welding is used very extensively throughout the aviation, shipbuilding, auto mobile and steel industries; this applies also to spray painting, electroplating, buffing, grinding, and many other operations. Sim ilarly with raw materials, various lands of acids, qfganic solvents, etc., are found in almost any type of plant For this reason there are certain industrial poisons which appear much more frequently than others and which may be found throughput the entire defense industry. Some of these are: Dusts Carbon Monoxide Hydrogen Sulfide Hydrogen Cyanide Sulfur Dioxide Oxides of Nitrogen Ammonia Phosgen Lead C'ftfrrnnm Benzene Toluene Xylene * Trichloroethylene Carbontetrachloride Carbon Disulfide Nitric Add . Chromic Arid Hydrofluoric Add Hydrochloric Add Sulfuric Add Others which are more directly associated with specific industries are: Trinitrotoluene (dust and vapors) Ammonium Picrate (dust) Mercury (vapors) Aniline ,- Radon Thoron As will be seat by examination of the above list some of these substances are pres ent as raw materials; others are final prod ucts, while a third group occurs as by-prod ucts generated in the various operations. Typical of the first group are the various acids, organic solvents, chlorinated hydro carbons, ampMipjt and carbon disulfide. In the second dass^vrevhave TNT and am monium piaster while, the remainder are commonly occnrring^duns, fumes, gases and vapors of a toxic nature generated in various industrial processes. While the theoretical possibilities for exposure to toxic substances in the above industries are far too numer ous for tabulation, this list represents those most commonly encountered. Dusts Silica-bearing inorganic dusts are prob ably found in all of the above industries. For example, mining of tiie iron ore in the sled industry presents exposures to free silica dust in considerable quantities. Buffing, polishing, and grinding operations done very Oi 39 b 9*^ s: !r g. ? ? ? P & { iF B .M \ ' i' \ Dust, Fumes, Gases and Vapors 59 extensively in a great many Industries; generate inorganic dusts; which for the most .port consist of "aluminum oxide and silicon carbide, hut also indude free silica in amor phous' and crystaline forms. For the purpose of quantitative determina tion, dusts may be divided roughly into three classes; as follows:' 1. The inorganic type such as -free silica and asbestos, which is collected and the num ber of particles per unit volume of air deter mined microscopically. of dust are by means of electrostatic pre cipitators (3) and various types of "grab" samplers. With the electrostatic precipitator, the dust is collected in a dry state and either weighed as is, or suspended in water and counted in a manner similar to that em ployed with die impinger method. Several of the grab samplers have microscopes in corporated with the sampling device and these are calibrated in such a maimer that the number of particles per. cubic foot of air can readily be obtained by almost instantan eous readings (4). 2. Organic dusts of natural origin, the amount of which is usually determined by Organic Dusts (Natnral) weight Typical of these are tobacco and flour dusts. This group as a rule is not classified by medical authorities as fibrosis producing 3. * Synthetically manufactured organic dusts, and hardly warrants any discussion compounds which may occur in the form of in this paper. While claims do exist to the dusts, such as TNT and ammonium picrate. effect that some dusts in this class have These substances when present as air con produced respiratory irritation, bronchitis, taminants in low concentrations are generally asthma, etc, these dusts are generally looked evaluated quantitatively by chemical- means. upon as nuisances rather than occupational disease producers. No official physiological Besides above types, there are also metallic threshold limits have'been established and dusts such as lead, zinc, cadmium, manganese, sampling of this type of dust for the purpose etc, some of which will be discussed under of evaluating an occupational disease hazard . another heading. has little or no meaning. Inor'ganic Dus<ts , The most common method for evaluation of this type of dust is to collect air samples in liquid solutions by means of an itnpinger (1) and to make the quantitative determina tion microscopically. When: calculating (he dust concentration, usually expressed in num ber of particles per cubic foot ;of air; the microscopic calibration factor, the volume of the sampling -liquid, and the size of die air sample, are taken into consideration. The sampling procedure; microscopic ar rangement; and calculations are extremely simple, but die actual counting is a tedious job associated with severe eye strain and requires considerable experience before dust counts can be relied upon. In' recent years the microprojection method (2) has been used for counting of impinger samples. With this method in which die microscopic field is pro jected on a translucent screen, die eye strain experienced in direct microscopic work, is eliminated. ' Other methods for evaluation of dus type Most of these dusts; however, are ex plosive when dispersed in certain proportions in the air and require control from this point of view. Considerable work to establish ex plosive limits for this type of dust has been done by the. United States Department of Agriculture. Synth*etic Dusta In the manufacture of TNT and ammon ium picrate; both of which represent basic war industries, we are confronted with toxic raw materials as wdl as' hygienically injuri ous final products.. In this industry great quantities of toluene;-.anhydrous ammonia, sulfuric and nitric adds are used, all of which are dassified as industrial poisons. TNT and ammonium picrate are themselves systemic prisons as wdl as skin irritants known to have produced fatalities and severe cases of dermatitis. A method for sampling and determination of TNT wafe-described recently by Pinto and . Fahy. (5) This procedure calls for the use of 10-c.c. of isopropyl alcohol in.the midget i M m m 60 31st National Safety Congress impinger. The chemical determination is The small ekctncainent produced .bythe. based on tiie reduction of TNT to triasnoor heat, of the^Wsktibn-- tiiro^^ toluene,and finally, at colorimetric compari couple is calibrated in terms ofcarfabnmon- son wiffa known standards. oxide concmtmtsoo': wltidi is-xeiul -dirtody Ammonium picrate is highly soluble in water .winch therefore can be used, as die collection medium in an' impinger When otnpKrigr for tiiis material -in industrial at mospheres. The deep color wbch results tqmn solution of ammonium picrate in water is also on tbe dial ofVnnlliamnieter.Thesource of snetionin tinsinstrumentis astnall centri fugal blower, the motor of vriudi is operated either from a built-in 6 volt battery or from a 110 violt lighting dretntthrongh a trans former. evident in extremely low concentrations and Another convemitot 'method for estimation for tins reason a direct colorimetric com of carbon moooxide thooghfess sensitiveand parison of the sample with known standards not -so- accurate is the nse bf paUalinm can be made: With this method there is a chloride anqtotdei. In tius.ractian.tix: paQa- possibility of interference from dimtrophenol, dhmr chloride, is reduced to'; metallic pal- . tiie extent of winch has not been determined lafiom body prixlncmg a stun, tfaebi- S). * teasty of which isin direct proportion to the amount of catbon monoxide in the atmos- Carbon Monoaridc ' phone undo' observation. Tbestain prodoced is compared to known, color; stanifards. &r Hus is a very time gas encountered in evaluation of tiie carbon monoxide. Resent various industrial activities. The toxic limit Tins method isnot specific for carbon mon- for tins gas is generally accepted as 100 oxide; however; three areiotheriedacmg p.pm. for prolonged exposure. To the pd- gases which also willprodace a.;Wain in the lic in- general its presence is most commonly presence`of palladium eMoritk-Inckkirtally, associated with automobile exhaust , and' gas the standard method tor .carbon monoxide hnwimg ajpImirM' ntilmnjr maimfarfwril.ggg evaluation, adopted by tiie British Depart- with a high percentage of. carbon monoxide. ment dflnduaUial RcWardi (7)~ccosb of a As a resnlt of incxq>lctecotnbastionit may palladinm chloridetestpaper thinm^ii Vhk'11 also be present when bunting natural gas the air tb .be ..sasqhd: is. driimbf niini or other fuds. In industrial operations .in of a handpurnp.Tbe stain timsprodaegdi* . volving fah'ng ovens, ' drying compared with a standard ^Idait^-^y ovens, blast furnaces, etc. carbon, monoxide is frequently enconntoed. hi industrial proc esses in general, and particularly where ' K Hydrogen Snffide ' diemical reactugiv'rare involved, carbon Hydrogensulfideis a very tarie gas with monoxide may be geopa^i as a^dangearous a disagreeable odor. It is fond.-&i na^yji^- by-product In prism'grinding, -which is dnstnal ^opai^tahs^wfaereV'-sti^^mr^i^d^ dosdy allied with tiie defense industry, a. compounds areused, bto;'.'jWbi>fu3iy.^pv'<toir,' high quality iron oxide rouge is reqinred. coimiered m/^la^fidd.jll^\^ljidmto?^inid < Occasionally >.-pwmfvriirfil petrokumindustriex. Sale. lambW^C -be on the premises as-bn adjunct to the prism tween 20 and 50 p.pm. by vttiamebave beeh grinding work. This involves tiie use of suggested by various Shite authorities in titis oxalic add for production of inn oxalate country. ' ry- - . , . - ' which is later decomposed by heat to yield, iron oxide rouge. In .thisr process carbon monoxide as wdl -as other gases.are gen erated. ; - * *<7 *.*?. / * . ` *viA . The . most rapid mrffrM for detdrauiatioo . of hydrogen sulfide is ondodbtedly the?use of1 a ~2iaod .operated* instrisiwnt.cqnrisHug csscntiallybf anaspirator bulband adetedorlT) Several methods have been developed.for - . tooettiroqgn wujCu ;ik. an.. the quantitative determination. of carbon The ' monoxide, bat onlytfaetwo most expedient . stance wln&viriim.in boto^ct.-witii `hydrogen procedures employed in industrial . hygiene work will be disaissed -here:. Onebfthese of wbi^:-a-ihi;'.propiqcl|qnj:fo tbeamonntof is tiie carbon monoxide indicator basal on 'lqrdnotBcn.':'sW|fi^;.~iKremecitV' xnd- caxif^be. nien*?' : tiie 'cata^tic reaction of - faopcalito which tmed on ah Wttothcd ?sriJe.'.'Ifcan'also,;be oxidires carbon monoxide to carbon dioxide. determined iodometrically/either by babb&ig Dust, Fumes, Gases and . Vapors 61 throogh a sodium hydroxide r solution and: For- die testing of sulfur dioxide, die dtradng with k)dii^ by bubbling through American Public Hcaith:;Assc|ciation (AJP. pottisumiodide itarchsolotioa and a meas- HA) (10) refers to aniodometriemribod ored amount of standhri iodiite'ra which re- (11) .by means of which.the air saniple is action the disappearance of the color indi passed through a gas wash botde containing cates tbeendpoint (8). a measured amount-of .standard .iodine; in potassium iodide-starch solution. The disap Hydrogen Cyanide pearance of the color qidtcatte.tee endaf-tee test, after which die amount of sulfur dioxide This gas for winch the industrial hygiene present can be calculated. - - bmeaMtfGaH<MTOa,Coonecticutand Mass achusetts havccstablishcd asafelinritof 20 p.pm. br yoltni^ is fooiod in dectro^ating dperad^.heat'treatin&etc. The British Department ofLidustrial Re search employs a starch-pofassnnh iodate test paper through whiebthe airsample is drawn by:means of a handpump. The' sulfur Aportable instrumentof the type ' dis dioxidc reduces the iodate tbiodinewiththe eased. in connection .with hydrogen sulfide; production of a stain the degree !o which is has been devdoped .for- hydrogen cyanide compared'to known odor standards. - dso.1 have been infonwSJ, however, that die hydrogen cyanide detector ni its original 1 formprovedless satisfactory and that it has Oxides of Nitrogen . beenwitbdrawn from themaricet temporarily This is .a gtqip of gases;, some of which pending further research. ' f * are extremely toxic. They are prodneed when nitric aad 'comes in contact; with, organic Chemical tests are .available for detection materials and cqrtain mebds j.dnring.dhmipal-' of hydrogen cyanide; such sis the Prussian nitration processes andburmng erf nitrated Mbeand'tttoaunte.reactioni- both,of. which.. materials; they are also present, in snail are ^tecific^di^ithis gas: hut allegedly not quantities during electrical.discharges m the sendee jdioo^p^fbr^coiicentntfioos encoun air. Above gases nay/ therrfor^Tie found tered in .industrial . hygiene work. Other in such industries and operationsas ammuni methods suitable^ foe, determination of .fins., tion works, ^photographic fihnnninnfacturinfc gas in'.small .concentrationsape .the Congo nitric acid plantvdectropiating : (bright led-rilvcr nitrate abd tfaebenridinie copper dipping),detooation of explosives, electric - . acetaietest papa&Tbese methods,1which welding, etc. ,have beenadopted ` as standard, tests by the v- ' nf -Research, During die chemicalreaihcxB&at accom are noo-spcrific, however, so that the possible pany above operatiaas, a mixture of. oxides interfarikeof othergascs snefa as HCL, are fanned.. The hazardous nature of this H*N,SOjaod HjS should be taken into, group; also called..<Utraus. fumes" is due,, cdhsddatioa.'' /' primarily to .the nitrogen dioxide,, a: reddish browngas whichreaets withwater and upon In* method suggested bythe Air Hygiene reparation forms nitricacid in the li Foundation. (AJLF.;) die air sample is ' -The result is often pulmonaryedema bthbled^ per.'' centpotassium frequently proves fataleThe fact teat hydroxidetafter which die determination is rejpntioa oi thqsegasesdoes not madebytitratingwitH diver nitrate (9). any immediate -discomfort in spit of teeir toxicity, makes teem doubly dangerous. A snmtr jjpiWB person may be exposed to these fumes and C-. experience only a slight respiratory irrito- eslo sdfur-dioxide ;gas are contr .. tko immsliatdy foUowing Hte exposure, mon in tbepetroleum industry.Tiiber works, while tee cate may devdop into a fatalcon- andsulfuricacid;. manufacturing. ^Sulfur dioxide is also encountered in booeandglae *dtion by next.dar- . workvmagnesium ,foanaries,and:od>er.' in-. For example, I know of a case rn a nitric dustries where sulfur;1 compounds-,are ,use<L. acid plant where a man was . engaged in Itisani extremay irritating gas, for which' filling nitric add into carboys in a" depart a duxsbdd litmt ^ lO puiuiL lias t^ sug ment with a wooden floor. One of tlte car- gested. '-V,. boys accidentally bndoe causiiig tee add to ' p) 62 31st National Safety Congress flow over the wooden floor producing the ical industry. It is a strong respiratory irri with si brown nitrogen dioxide gas in great volumes. tant for which safe limits ranging between The operator not being familiar with the 50 and 85 p.pm* have been recommended toxicity of this gas and experiencing no im (Russian investigators 13-39 p.pjn.; State air pe probla other 1 mediate physiological warning, remained on of Massachusetts 50 p.pjn.; Flury and cubic f the job attempting to dean the floor by mop Zemik 85 p.pjn.). \ task; < ping np die add, instead of leaving the work meat i place for fresh air. As a result a consider Ammonia vapors can be evaluated directly casein able portion of this gas was probably inhaled. in the field by bubbling die air sample is joist He became seriously ill a few hours later through a measured volume of 0.1 N hydro limit; and died within 48 hours. Cases of men be chloric acid in water solution using pbenol- air. F< coming sick while doing dectric wdding in phtbalein as an indicator; the appearance of imping side tanks or in other confined spaces are a pink color indicates the end point From . handle often referred to in the literature. Many of the amount of add used and the size of the lead u these cases are undoubtedly due to oxides air sample, die concentration of ammonia quires of nitrogen generated in the dectric arc. vapors can be calculated (8). and cs While there are several methods known Sulfuric add canjalso be used with above pletioo fi for die quantitative determination of oxides method. In another method, recommended of nitrogen, testing for these air contaminants by the AJMLA, the air sample is collected is not so simple as that for some of die. in sulfuric, add, but the final evaluation is others discussed in this paper. Incidentally,., made in the. laboratory by standard analytical in view of the cumbersome procedures in-1l means. volved in testing for these gases, the amount of ventilation required for their control after blasting in mining and tumid work is some Lead times based on die amount of carbon mon Exposure to this metal I occurs very extea- The (U.SJ with r concei air. oxide present, which can readily be deter sivdy in nearly all types of mamifadqritig. mined.'With explosives designed for a low The most-frequently encountered' forms of oxygen balance resulting in a relatively high lead ar finnes, dust and dispersed pigments. carbon monoxide concentration and corre- These occur around lead melting operations, spondingly low volumes of oxides of nitrogen, 1 soldering, wdding of metals covered with this is a safe and expedient procedure. lead-bearing paints, and; in spray; painting work. For actual detection of nitrogen dioxide,* die method employing starch-potassium Sampling of lead-contaminated atmos Iodide test paper is probably die best known. pheres Is.usually done either by means of This paper when damp is colored blue in the tiie impinger or by the electrostatic predpita- presence of nitrogen dioxide^ The method is tor. When the impinger is used, as is fre non-specific, however,lOther,1) specific meth quently the case whim investigating spray ods for evaluation of nitrogen dioxide, and painting and many other types of work in sensitive at low concentrations are die Griess- volving lead dispersion, the sampling liquid The ing of well a propei rahun in sw ing a well a volvea are pi mium Canad were ..ing d X Ilosvay and' the Bismarck Brown tests. With both methods, die air sample is bubbled through chemical solutions .titter which the quantitative determinations are made in die laboratory by colorimetric analysis. Although physiological safe limits up to. 40 p.pjn. have been proposed for these gases, atmos pheres which by odor or color'indicate the may be other dhtilled water or dilute nitric add ? Regardless of the Collection method used, the final evaluation of`the amount of lead present is done in the.laboratory by various analytical methods, the description of which is beyond the scope of this paper. It prob As mium the i 1 medio prerii labor; analyt presence of nitrous fumes should always be ably should be emphasized, however,, that al viewed with suspicion. though-some of these methods are highly sensitive and the.experienced analysts usual At otlt tl Ammonia ly weUrtitined to handle minute quantities of lead in thdr work, it is preferable to take impiii than large air samples wherever possible to.fa&l- shod* As stated elsewhere, ammonia is an im itate the laboratory work. With the huge coopt portant raw material throughout die chem impinger and the dectro-static precipitator lected *> ... ,t,-.* .t */, Fumes, Gases and Vapors 63 c. a-n. a. a fic u r < r 7 s , r 04 erj j* s,y* r with sampling rates of 1 and 3 cubic feet of Mercury air per 'minute respectively, this is not a. problem. With the midget impinger, on the The present emergency has greatly accel other hand, with a sampling, rate of only 0.1 erated the use of mercury,'not only in our cubic footper minute, this becomes a tiresome ammunition works;, but also in many other task; especially if tiie handcranked instru plants directly or indirectly connected with ment is used.'Let us take, for example; a the defense industry. In some cases entirely case in which the atmospheric lead dispersion new uses have been introduced for tins metal. is just about on die border line of the safe For example, a recent development is an limit, i. e. 1J5 mg. per 10 cubic meters of anti-fouling paint containing' merctuy, now air. For a 30 minute sample with the midget used in our shipyards. Application of this impinger, only 3 cubic feet of air have been . handled. This represents only 0.013 mg. of lead in die air sample, which evidently re quires a- fairly sensitive analytical method and careful handling for a successful com pletion of the test merenry-bearingjpeunt by means of spraying naturally introduces a serious exposure to mercury poisoning and calls for careful con trol;. this applies also to tire manufacture of the paint Due to the great demand for mercury and the shutting off of foreign sup. plies, many old mercury mines are now being reopened so that refining of this metal with Cadmium . accompanying occupational disease hazards has expanded considerably daring the past year. The United States Public Health Service (U3PAS.) (16) suggests as a .safe limitwith respect to toxidty of cadmium fumes a concentration of 1 mg. per 10 cubic meters of air. The toxic properties of mercury as a respiratory hazard when present in tire form of vapors or in a finely divided metallic state are probably fairly well-known to most men The metal is used extensively as a coat ing of iron and steel for rust prevention, as well as in structural steel to impart certain properties. Exposures to cadmium and cad mium-fumes may, therefore, be .encountered in such operations as electroplating, weld ing of cadmium-bearing iron and steel as well as many other-processes where work in volves cadmium-plated articles. Some of yon concerned with industrial health. A safe limit; toxicologically, pf about 2 mg. per 10 cubic meters of air appears to be generally accepted for inhalation exposures. Althouh the metal has a relatively low vapor pressure at or dinary temperatures, investigations have drown that sufficient vapors are emitted to produce a mercury hazard in rooms where this material is used in metallic form. are probably familiar with die cases of cad A number of methods are available for the mium intoxication in a plant in Ontario, evaluation of mercury vapors in air. One of Canada, a few years ago, when 14 persons the most expedient procedures is probably by were poisoned--two fatally--during anneal- means of the Nordlander apparatus utilising -ing of cadmium plated rivets (17). a selenium sulfide test paper, the color 'of which darkens in the presence of mercury. As in the case of lead, sampling, for cad The amount of mercury present is estimated mium fames or dost may be done either with by comparing the degree of darkening with a the impinger (with water as collection standard c&or chart. medium--A.P.ILA.) or by the electrostatic precipitator and the samples evaluated in the Another more recently developed method laboratory by gravimetric or colorimetric involves an optical instrument based on the analytical methods. opacity of merchry vapors to ultra violet light of a. certain wave length. lit this instrument, At this -point it probably should be brought therefore; when ultra violet light of a specific out that for sampling of metal fumes, the wave-length is directed towards a phototube, >f impinger has a lower collecting efficiency interfering mercury vapor will reduce the e than the electrostatic precipitator, which light received by the phototube and conse [- 'should be taken into consideration when quently also its current flow, which in turn e comparing results obtained on samples col is calibrated in terms of mercury concentrat - if lected with the two instruments (18). . tion. This Instrument is not specific as it is r or a a r u XI f i I1 SI3 ?.' * '.*"** : ` ' 64 31st National Safety Congress subject to other light intercepting media such tible-gas indicator is far more expedient. as smoke and fog. Most of these devices, used primarily for tire There are also.other methods for determin ' prevention, work; are designed to read to ations of mercury, entailing condensation of within 1% of tiie lower explosive limit of tiie tiie vapors and subsequent electrolytic deposi gas or vapor under test For above sub tion of the metal, chemical reaction methods, stances . with lower explosive limits around etc. The first two mentioned above, however, 1$ by volume, this means that concentrations are the most expedient and yield immediate down to 100 p-p,m.an be detected^ which U results during the field investigations. approximately the accepted toxic limit-for these solvents. For benzene with a safe limit Benzene, (Benzol). Toluene and Xylene of 75 p.p4n. (19) a modified combustible, gaa indicator has been placed on the market^ These three aromatic hydrocarbons are widely used as industrial solvents and ingredi ents in a number of chemical reactions. Tolu ene, for example; is an important raw mate rial in our ammunition manufacturing, espe which measures concentrations ranging/be* tween 0: and 1000. p-pjn. A spectroscopic method for determination of benzene and toluene in air has been described by Cole (20); 0. cially in the production of trinitrotoluene. Chlorinated Hydrocarbons With the increased demand for toluene and the corresponding scarcity of this material, Of these, trichloroethylene and carbon benzene is rapidly takpig its place as a sol- 1 tetrachloride are probably most frequently vent in many industries.7Xylene; which besides found. They are used extensively as metal being an important solvent, also does enter as deanutg agents; the former in legato de- a raw material in certain chemical processes, greasing machines on a production 'basis arid at present associated with the defense industry ' the fatter for work of a more occasional and therefore used in great quantities. For nature. These materials with their grease instance, in a plant I visited recently xylene dissolving properties are regarded by medical is used in the production of a certain type of authorities as very injurious to tiie fatty-tis resin, which in torn is employed in an article sues of the human body. manufactured for the United States Army. As in tiie case of other substances referred All these three materials are classified , as to above, there are chemical methods for- industrial poisons, although there appears to quahtitative determination of vapors, from be some confusion as to the relative toxicity these materials; but they'are mostly too ccm- of each. Benzene is generally considered as bersomc for routine sampling. Optical instm- tiie worst offender, although this may not be ments are available, however, for rapid evalu- doe to a greater toxicity of tiie material per atioa of sudi vapors dispersed in the air. The se but to tiie fact that it has a higher;vapor best known of these is probably tbe portable pressure than tiie other two so that for a interferometer in- winch the. difference be given temperature more of it will be|found tween tiie refraction of air (tiie comparison in tiie air. However that may be,' tiui toxic substance) and that of tiie gas mixture to be effect of all of them, once dispersedlin the examined (is measured. ''This difference is air, is generally, recognized and therefore in calibrated in-terms of-concentration of tiie dicates the need for strict control- wherever gas or'gases under observation. Naturally they are used. tiie same, readings will be obtained for all gas For the evaluation of these materials some chemical as well as physical methods are available. Most of tbese; however, are com plicated and cumbersome, involving such operations as nitration by bubbling tiie air through nitric add with subsequent colorimet ric determination, or condensation pf tiie mixtures resulting in tiie same iefractive mdex, so tbe instrument is therefore not'spe' cific. With information, however, as to the type of air contaminant concerned in a. par ticular problem it is an exrerdjingly useful instrument applicable to the investigation of.a great variety of gases and vapors. vapors fallowed up by laboratory analytical procedures for tiie. filial evaluation. ! While Carbon Disulfide methods of this type may be satisfactory for This substance which at ordinary tempera stientific purposes, for routine sampling in tures occurs as a liquid with a high .vapor control work in industrial plants, a'combus pressure; generates, toxic vapors for which' rdativ by var have t 3 p.ps Britts! trfal 1 p.p.m. 20 p.p betwee the p posure Aid in a g found indust raw in For Hygie tbe aii droxkl thatei Britisl trial. 1 consist ethyfai oredc pared mahjltl their c .be hr Ubforl these i low e safety In hydro! aretii tfame;. other ; resold nasal.chrotn mg. pc lished worici Hydrc istin: bydrpi of3p. while, fatter. San adds": sodiun .<n~ ...^v Dust, Fumes, Gases and. Vapors 65 relatively low safe limits have been suggested through potassium hydroxide; and hydro- by various authorities. Russian investigators' chloric add through glycerol-potassium car have recommended a threshold limit of only bonate-water solution. For the .final labora 3 p.pjn. for prolonged exposures, while die tory. evaluation I refer jto standard methods of British Department of Scientific and Indus the A.P.H.A. trial Research has suggested a value of 10 ' p.p.tn., and our. own State of Massachusetts, Bibliography 20 p-p.ni. While there is a wide divergence between these values,jgiey all tend to indicate, die potential dangers connected with exposures^ vapors of carbon disulfide. Although this stdvent.may be cocoontered in a great many industrial operations, it is found primarily in' die visCbse--and rubber industrial where it constitutes an important raw matoiaL. ., ' For evaluatioo of these vapors, the Air Hygiene Foundation- recommends drawing the air through an alcoholic.potassium hy droxide solution to form potassium ethyl xan- 1. Greenburg, L. and Smith, G. W. A New Instrument for Sampling Aerial Dust R. I. 2392*U. S. Bureau of Mines,. 1922. 2i} Brown, Carlton E.; Baum, Lester A. H.; Yant, William P.,. and Schrenk, HelnuxthH. Microprojection Method for. Count ing Impinger Dost Samples. RJ.3373, U. S. Bureau 'of Mines; January, 1938. 3. Barnev E. C. and Penney, G. W. An Electrostatic Dust Weight Sampler. Jc, In dustrial Hygiene & -Toxicology, 20, 3, pi 259 March, 1938. thate which is determined iodocbetrically. The 4. Bernz, N. R. Dust Counts and Their British Department of Scientific and Indus Significance. Heating, Piping and Air Con trial Research. uses a colorimetric method ditioning, March, June and October, 1942. consisting of bubbling the air. through dietbyiaznine and copperacetate forming a col ored coImpourkL the intensify of which is com pared with standards. In view of the inflammahQify of these vapory a. rapid method of their evaluation in high concentrations would ' 5.' Pinto, S. Sherman and Fahy, John P. A New Colorimetric Method for tiie Deter mination of T.N.T. (2, 4, 6 Trimtrotdaene) in Air. Jo. Industrial. Hygiene-& Toxicology, 24,2, p. 24 February, 1942. .be by. means of a combustible gas indicator. & . Sands, Frederick. W, 189 Claremont Unfortunately, bowever.-the sensitivities of - Avenue, New York; N. Y. Unpublished data these instruments as built at present; are not obtained through personal communication, low enough, to gct'withmthephysiological Avgust 1942: safety range of tins materuL 7. Department of Scientific and'Industrial Research, London, England Methods for De Adda tection of Toxic Gases- in Industry. In titis- group- prohgbly nitric,. chromic; hydrofluoric; Hydrochloric and sulfuric adds' are -those most, commonly, encountered, df thesev.tntrk add has becn discussed under an Leaflet-No. 1--Hydrogen Sulfide Leaflet No. 2--Hydrogen." Cyanide . Leaflet No. 3-^-Sulfur Dioxide Leaflet Na 4-jBenzene other 'heading. ..|Kqppsares'; to. chromic add Leaflet - No. 5--Nitrous Fanes resulting in chrome deers and the perforated nasal., feeptiud are frequently; found, around - Leaflet No. 6-rCarhoa-Disdifide Leaflet Na 7--Carbon Monoxide "chromiumplatingtonks.' Asafelimitof 1 LeafletNa.S^-Phosgen mg. per 10 cobic.inetersof air basbeen estab- Leaflet Nd 9--Arsine lishcdfor chrbmk add which in electroplating > . Leaflet N* 10-rChlorine workoccursasa oust oyer the plating baths. leaflet Na 11--Aniline fl Hydrofluoric and hydrochloric adds also.ex- Leaflet Na 12--Organic Gompaunds a- ist ih gaseous form as hydrogehfluoride and 8. Method employed at the Harvard hydrogen chlonde respotiyely. A safe limit School of Poblic Headth: i- of'3 pipjh. has been suggested for.the former, wh3e .it has been set at 10 pipuh. for tiie latter. Sampling'far nitric,.chromic; and sulfuric 9. Air Hygiene Foundation of America, Inc. Preventive Engineering Series,".Bulletin No. 2, Part 8. c adds is usually done by babbling through a 10. Cook; .Warren A. Report on Methods h sodium hydroxide solution; hydrofluoric add for Determination ofPoisooous Atmospheric i i; i S',-! 1 lili i^fl 66 31st National Safety Congress Contaminants, pp. 80-85, 1935-1936 Year Book; American Public Health'Association. 11. Fieldner et al. Jo. Industrial & Engi neering Chemistry 11:519, 1919. 12. - Evans, R. D. Apparatus for the Deter mination of .Minute Quantities of Radium, -Radon and Thoron in Solids, 'liquids and Gases. Review of Scientific Instruments, <$:99 --112 (1935). . 13. Brown, S. C; Elliott; L. G.; and Evans, R. D. Detection of Radon by Means of A Proportional Counter. Review of Scien tific Instruments 13: 147--151 (1942). 14. Evans, R. D. and Goodman, C De termination of The Thoron Content of Air and Its Bearing on Lung-Cancer Hazards in Industry. Jo. of Industrial Hygiene & Toxicology, 22, 3, pp. 89-99 March, 1940. 15. Evans; R. D.; NSson, S. J.; Good man, C; and Bemz, N. R. Industrial Ap plication of a Method for Determining ibe Thoron Content of Air. Proceedings of tiie VIII International Congress ot^Occupational Diseases and Preventive Medicine, held at Frankfurt a. M. Germany, September 26-30, 1938. 16- _ United States Pnbllc Health Service, Division of Industrial Hygiene; . National Institute of Health, Washington, D. C Cad mium Poisoning. Public Healtil Reports 57, 17 April 24,1942. ..... 17. Bulmer, F. ML R.; RothwcU, H. E.; and Frankish, E. R. Industrial Cadmium Poisoning. A report of fifteen cases, includ ing two deaths. Canadian Public Health Jo. 1938, V29, 19-26. 18. Littlefidd, J. B.; Feicht, Florence; L. and Schrenk, H. H. Efficiency of Impingers for Collecting Lead Dusts and Fumes. R.I. 3401, U. S. Bureau of Mines; May, 1938. - 19. American Standard Association. Ben zene; allowable concentration. Z 37.4* 194L 20. Cole, Peter A. Determination of the Concentration of Benzene and Toluene in Air by a Spectroscopic Method. , Jo. Optica! Soc. Am. 32,304-306; May, 1942. Selection, Use cmd Maintenance ol.Hespiratory Protective Devices* . ByH.H.SCHRENK Chief Chemist, Health^Division, Bureau of Miwi and S. J. PEARCE Associate Chemist, Gas and .Dost Section, Central Experiment Station, Bureau bf Mines, Pittsburtfi, Pai) Pobluhed br peraistiou of the Director, Bnrcxa of Mines, U. S. Department of the Iatetiar,~Wasb- ington, D. C. 1 ' ure or improper use of other control equip ment H. H. Schrenk; chief chemist; Health Di Respiratory protective devices usually,are vision, Bureau of Mines and employed to supplement other methods of . control, as a temporary expedient, or when, S. J. Pearce; associate chemist, Gas and other methods are not readily applicable or Dust Section, Central Experiment Station, . practicable. It seems reasonable to assume, Bureau of Minesi Pittsburgh, Pa. -however, thaf where respirators are used, There are several well-recognized pro cedures for controlling exposure to hazard ous atmospheres in industry. They include (a) substitution .of .less toxic-material; (b) enclosure of processes,- (c) wet methods; (d) local exhaust; (e) general ventilation, consideration has been given to the tutors involved, and that the derices can provide satisfactory protection if used properly. Thor use should not be arrived at simply , by a process of elimination of other methods that are more difficult to apply. end (f) use of respiratory protective de Atmospheric contaminants indude gases, vices. In addition to their employment as a vapors, dus^ fumes, mists, and fogs. Res control measure in .occupational exposures,, piratory protection against these contamin respiratory protective devices also are essen ants may be required for concentrations? tint - tial in emergencies that may arise from fafl- are immediately dangerous to health or life 555? s *sy. rtp-v f. > p' ^ I.C ' 'O T IL J*' 'W F ? r /tori, 'Fumes, Gases and . Vapors 67 after comparatively short exposures, or that may*produce injury.only after prolonged, or repeatcdexposures. Also, it may be necessary to use such devices against a angle type of contaminant, against a combination of various types, or in atmospheres deficient in oxygen. n To meet the conditions mentioned, various types of respirators have been developed Two basic principle?. have been utilized in their development--purification of the in haled air by removal, of the contaminant (airpurifyingxespirators) and supplying a respir able'atmosphere to the wearer from an uncontaminated source (atmosphere--air or oxygen-supplying respirators). Air-Purifying Respirators 'Air-purifying' respirators include canister gas masks and chemical cartridge respirators for removing gaseojts contaminants and me chanical-filter respirators for removing par-. ficulate matter or dispersoids. Canister gas masks and chemical cartridge respirators may be equipped with filters for removing dis persoids, thereby giving protection against both gaseous and particulate contaminants. As these devices, provide protection only by removing contaminants, it is obvious that sufficient oxygen must be present in die atmosphere to support life. A canister gas mask usually consists of a foil facepiece connected by a flexible breath ing tube to a canister that nay be carried in a harness on die chest; under die arm, or oh die back. The canister contains die materials for removing die contaminants and purifying die air. These materials remove the contaminants either by chemical.reaction Or by physical absorption, as cm activated charcoal. As no single substance has been discovered that will remove all types of gaseous contaminants, the canister fill de- pends on die type of contaminant against which it is designed to protect Fortunately, materials . are available that will protect against groups of compounds; therefore, a multiplicity of materials is not' required.1 For example; activated charcoal will absorb organic vapors, and alkaline materials such as soda lime and causdte will , remove arid gases. Ammonia may be removed by silica gel or by various materials impregnated with such substances as copper or cobalt salts. Carbon monoxide is removed by catalytic oxidation to carbon dioxide by Hopcalite, a special preparation of manganese and cop per oxides. The. protection that a canister affords depends on the material with which it is filled. For example; a danister may be filled with activated charcoal alone and give protection only against organic vapors, or. it may be filled with all types of the mate rials mentioned and give protection against all -gaseous contaminants. For protection against a single contaminant the use of a single absorbent is desirable, as the life of the canister is longer, thus providing more economical protection. It' is therefore extremely important to' know the* contaminants against which a canister will protect To assist users in easy identification, a classification' of gas-mask canisters has been developed in conjunction with a color code. Tins code, which is an American standard used by all manufacturers of gas masks' in the United States, is as follows: Canister, type letter Contaminants prpctccted against-- Colors A B C; .D AE,etc. AB ABC N Add fpses ._.____ ...... White.* - Organic vapors-------- Black.* Ammonia __________ Green. Carbon monoxide -- Blue. v Dusts, fumes, mists, fogs, and smokes in combi One-half inch contrasting black nation with any of the above gases or vapors or white stripe qround the can ister near.the top. Add gases and organic vapors-------------------- Yellow. Add gases, organic vapors, and ammonia -- Brown. All of the above atmospheric contaminants.-- Red. # Filters are included in this canister, but stripes to indicate them are unnecessary. . C*nistert for a tingle ns or vapor other than, ammonia or carbon shall have a $.fnc& .colored stripe around the camstrr near the bottom. The color of the stripe 31 be assigned. v: .* 1 m y * '* TT* } vt il` T.i^AVji'-."; 68 31st National Safety Congress Canister gas masks have been developed tiie amount of permissible leakage depends primarily for protection against atmospheres on the toxicological significance of- tiie mate immediatelyjdangerous to life and are used rial. Therefore various types of filters are mainly in emergencies. Therefore, .first.con used; tint is, a filter may be satisfactory sideration has been given to complete respira for silica dust and not satisfactory for a tory protection to prevent even momentary toxic dost such as lead or cadmium, owing failure that might result fatally. These to thegreater toxicity of the latter. A filter masks, however, are not designed for pro that b satisfactory for dost (mechanically tection against extremely high concentra generated, as by grinding) may not be satis tions, and in Bureau of Mines Approval factory for fume produced by heating .or Schedule 14E concentrations are limited to burning, as in lead burning; owingto par- two per cent by volume, with tiie'exception tide-size differences..On the other band,.a of ammonia, for which the limit is three filter satisfactory for silica dust is considered per cent The service life of the. canister satisfactory for all other fibrosis-producing depends on the individual characteristics and dusts and nuisance dusts; and a filter con the amount of absorptive material"used. Al sidered satisfactory for lead dost b con though these masks are designed primarily sidered satisfactory for other toxic dusts, for emergency use, they will, of course,' give the toxicity of which does not exceed signif good protection for non-emergency., situa icantly that of lead.' tions, and filters may be incorporated to remove particulate matter. Mechanical-filter respirators have been de signed. for protection against atmospheres Chemical cartridge respirators usually con sist of a small cartridge or canister attached directly to a half-mask facepiece. The mate that are not immediately harmful; there fore primary consideration' has beat given to lightness, compactness, and comfort rials for removing the contaminants are the same or similar to those used in canister Atmosphere-Supplying Respirators gas masks, and filters may be incorporated to remove particulate matter. These devices may be considered small gas masks and are designed for protect!6n in atmospheres that could be breathed by workmen without pro tection, but that might be irritating or dis agreeable or produce injury to health after ' prolonged or repeated daily exposures; hence, primary consideration has .been given to light ness, compactness, and comfort Respiratory protective equipment that sup plies a respirable atmosphere from a source independent of tiie wearer's immediate atmospheric. environment b of two bask types--* hose type, in which air from an uncertaininated source is conveyed to the wearer: through a hose or tube, and a self-contained type, in which a supply of oxygen is carried by tiie wearer. The air-supplying respirators commercially Mechanical-filter respirators usually con available, may be divided into three types: sist of a filter arrangement of some fibrous Hose masks, air-line respirators,'and abra material such as frit dr paper, in a holder sive blasting helmets, hoods, or masks.' connected directly to a half-mask facepiece. The filter consists of fine fibers crisscrossed ' Hose masks consist of a tight-fitting, foil to form a maze or. intricate network of facepiece; breathing tube or bits, a harness, tortuous passages. The dust fume, mist and a comparatively large-diameter, noncollap- fog are removed by physical trapping when sible hose line; and. a hand-operated blower. the air is drawn through this material. The The harness and hose are strong chough for filtering efficiency increases as the dpst load retrieving the wearer in an emergency, and on the filter increases. The service life of the the hose most not collapse under heavy filter, therefore, does not depend on recogniz weight and must not lank; The maximum able leakage, as does tint of the gas masks, - length of hose approved by the Bureau of but on increase in resistance of the filter to Mines is ISO feet The use of a hand-oper a point where resistance to inhalation be ated Mower assures that ra second person comes excessive or uncomfortable. Although will be present, in the. event of difficulty. the filters will remove all types of particnlate Also; tiie attachment of the . hose-to the matter, the extent to which the material b blower and tbe large diameter of tiie hose removed depends cm the characteristics of 1 permit breathing without undue resistance, the particles, sdcfa as size- and state. -Also. even though;the Mower b hot operated. The. a 9. T*J* Y f f t J L i7 ^ ,fc;*H d 5 i < 3 3 ? g ` () Dust, Fumes, Gases and Vapors 69 Intake to the blower most be in uncon- oxygen breathing apparatus. These apparatus ^TwinatfNf air. .consist of a cylinder of compressed oxygen, Hose masks ate- sturdily constructed, as they are designed to be worn in atmospheres immediately dangerous to life and' to afford protection against ail types of atmospheric contaminants and atmospheres deficient in oxygen. a reducing valves an admission valve^ a breathing tag, breathing tidies and mouth piece with valves for direction of inspired and exhaled air, a regenerator for removing carbon dioxide^ and a cooler.' They operate on a closed-circuit principle, and the. entire device is worn by the user. -When the cylin Special-type hose masks. without blower and generally used with about 25 feet of hose also are available. Although the hose, breathing.tubes, and facepieces are essentially die same as those for hose masks with a blower, the harness is modi lighter and die device is designed for lightness, compactness, economy, and simplicity of operation.' Such masks are designed' for non-emergency use or for use in atmospheres not immediately dangerous to life. der valve is opened the oxygen flows through the reducing valve, thence through the ad mission valves into the breathing bag, until die tag Is expanded to a point at which the admission valve automatically cuts off-tire supply oxygen. Oxygen is breathed from the hag' and the exhaled air passes through the regenerator to permit removal of carbon dioxide^ thence through a cooler, and tack to the bag. As oxygen is consumed, the tag tends to collapse,'and the admission valve, automatically admits additional oxygen. Air-line respirators usually consist of a high-pressure air-supply system, a hose of relatively small internal diameter, a detach able coupling, and either a full or halfmask facepiece, or even a helmet or a hood. As tbe air for this typeof respirator usually is supplied from a high-pressure compressed-^ air system, it must be checked to see that it does not contain objectionable or harm ful contaminants. Dust from dust, oil mists, Self-contained oxygen breathing apparatus give respiratory protection, against all types of atmospheric contaminants in any concen tration that can be endured by the skin but require gas-tight goggles in atmospheres irri tating to the eyes. They also protect .against atmospheres deficient in oxygen -and are designed for protection against atmospheres that are immedtateiy dangerous to life. odors,- and even carbon monoxide may.be present if the compressor becomes too hot; therefore, critical attention should be given - Selection of Respirator* to-the air supplied to these devices. -The?use of respiratory protective devices' Although this respirator will give respira tory protection against all types of contam inants, it is designed for routine protection against concentrations ofcontaminants tint are not immediatdy dangerous to life'or health. It Is- thus limited, owing to the pos sibility of leakage around the half-mask facepiece and also to the fact that no pro as a control procedure requires as much consideration as any other control method. In the selection of a respirator, thorough consideration should be given to various factors involved, st&h as:. a. the chemical, physical, and toxicolog ical properties of the substances against which-: protection is required vision is' made so that the. wearer can breathe b. fbe effect of tire processes and condi respirable' air, should the air supply faQ. tions frf ose of the substances as they relate -Abrasive blasting respirators are essential ly air-supplying respirators that have been to. tire `possible formation of significant sec ondary products modified by the addition of a suitable cover c tire processes and conditions of their ing to protect the head and sbotdders against use they relate to the dissemination of impact and abrasion by rebounding material. contaminants They are designed primarily for rise in abra sive bifasting operations and not for use in atmospheres that are immediatdy dangerous to life. <L an evaluation of actual and potential -hazards to determine whether conditions im mediately dangerous to life or health might arise or whether Injurious effects would be The most common devices for supplying produced only, after prolonged or repeated oxygen to 'the wearer are self-contained exposures & Pw m *&&**?- 31st National Safety'Congress e. feelfiture of the duties" to be per with blowers and gas masks. Owing to formed by the wearer of protective devices their weight and maintenance and training as they relate particularly to restriction of requirements, .oxygen breathing apparatus movements probably would not be used. The hose mask t an understanding of the principles, de sign, scope of use, limitations, advantages, and disadvantages of the respiratory protec tive equipment available would be satisfactory and might be chosen if the encumbrance of the hose line were not too great The most probable dunce would be a gas mask, because of its light weight, ease of maintenance; and the small amount of Virtually all applications of respiratory ' training required by the wearer. The appro protective devices are spedfic^asd require priate canister should, .of course; be chosen. individual attention. Examples typical conditions with indication orchqice^ appro priate respiratory protection arc giyen. Low concentrations are atmospheres -that. can be breathed without protection but that will produoe discomfort and posable chrome Atmospheres deficient inNwygen may be injury.after repeated exposure to diem. Hose extremely hazardous and immediately dan masks and oxygen breathing apparatus would gerous to"life. Only oxygen breathing appar give satisfactory protection, but they would atus or a hose mask with blower should be be given.litde consideration for such a situa chosen for protection under such conditions. tion for die reasons' already outlined. Gas Final choice between these two devices will masks,-chemical cartridge respirators, or air depend on working conditions. line respirators would be satisfactory. Final choice would depend on actual conditions and For example, for rescue work in mines, freedom of movement required by the worker. die men must proceed for considerable dis tances from a source of fresh air. Obviously, For pneumoconiosis-producmg and nuisance hose masks would hot be satisfactory, as dust, air-line respirators and pnemnocoaiosis- wearers are limited to a distance of 150 feet; ^ incing- and nuisance-dust respirators or therefore, oxygen breathing apparatus all-dfjSt respirators could be chosen. If die be used. However, for use in.entering cop- dust concentration Is exceedingly high, air- fined spaces, such as tanks and manhole^Uoe' respirators would, be preferable. If die hose masks are generally preferred because conJd:`it:i--ons ~ocf -w--o*r-k---a--r-e---s--u-c*h "as to int--eref--ere they are easier to maintain and relatively with the use of an air-line; mechanical-filter little training' is required to use diem. Air- respirators will serve satisfactorily, even' purifying devices should never be worn in though they are awkward to wear for many atmospheres deficient in oxygen.. kinds of work. By very high concentrations is meant those exceeding two or three per cent Either oxygen breathing apparatus or hose masks with blowers are the logical choice; and again final selection will depend on working conditions. Although gas masks might afford some protection, they would not be-a good choice, because very high concentrations In dicate a confined space with possibility of low oxygen; moreover, ;the absorbents would be used up rapidly. The marked discomfort produced by such irritating gases'as am monia and sulfur dioxide and the danger of poisoning through the skin by absorption of hydrogen cyanide limit the concentrations that can be entered. Concentrations referred to here are those not exceeding approximately two per cent but nevertheless immediately dangerous to life; 'Oxygen breathing apparatus would, of: course; be applicable; as would hose, masks For toxic dust, air-line respirators, toxicdust respirators, or all-dust respirators would be a .logical choice. The final decision will de pend on local conditions of work and the ma terials being used. Knowledge of the concen trations likely to be encountered and of the safe or permissible concentration is necessary in evaluating the protection afforded. Fume Is particulate matter formed by volatilization and Condensation, as- in lead' burning. Fame is defined because it is a term used loosely to refer to gases; vapors, and particulate matter. Such usage is confusing and may lead to serious injury if a mechan ical-filter fume respirator is used for pro tection against some toxic gas or vapor against which it affords no protection. For fume as defined above, air-line respirators or mechanical-filter fume respirators would be fee logical choice; and final decision would depend on local working cooditioos. Fo filter to ti and l head! Dust, Fames, Gases, and Vapors 71 Frequently protection must be afforded resistance to inhalation indicates that the against a combination of gases and particulate' filter should be cleaned or renewed. matter (dust; fume, mist, and fog). If the - " i atmosphere is not immediately dangerous to In the use of gas masks good facepiece fit life, air-line respirators are generally rec is also necessary, and the proper canister ommended. However, gas masks equipped must be chosen. As the wearer depends on with a suitable filter or cartridge-type respi odor or irritation to warn when the canister rators equipped with a suitable filter may be is exhausted, he. must be. acquainted with the used. Final decision not only would depend warning properties of contaminants for which on the local conditions of work as they relate to freedom of movement but also on thorough consideration toascertain whether gas masks or cartridge respirators would give die desired protection. protection is worn so that leakage will be detected readily, Rersons using gas masks in toxic atmospheres should have had pre liminary training in the use .and limitations of the equipment. Use of Respirators Although choice of a suitable respirator is important; other considerations are equally so. Obviously, if a respirator is to do the job for which it is chosen, it must be worn properly and be kept in good condition.. Fre quently persons do not know how to wear a respirator, and if it is not dean it is un pleasant to wear. Better protection and fuller cooperation doubtless would be obtained if the respiratory protective devices were kept under the supervision of a. responsible person who would see to .it that die wearer is properly instructed in the use of the device, that die device is cleaned and disinfected regularly, and that it is maintained in' firstclass condition. No instructions are necessary when bard bats or hard-toed shoes are given to work men; as they are used to wearing such ar ticles. Too frequently respirators are handed cut-in a similar manner. Even the simplest respirator is comparatively much more com plicated than protective hats or shoes and is a device that most- workers are not accus tomed to wearing. The principles on which each device is based, its field of use, and its limitations, as well as the essential parts, should be explained to the wearer in. terms he can understand;- Detailed instructions with practfce^SKSuld'lje given': to all persons who are expected to'wear such devices. Further, an explanation of the importance of wearing the respirator should be helpful in obtaining more complete cooperation. For example; in the use of mechanicalfilter respirators attention should be called to the importance of a good facepiece fit and proper but comfortable adjustment of the headband, and also to the fact that increased All respirators approved fay the Bureau of Mines are furnished with an approval label that gives concise information on use and linutations^Also, more detailed instructions that .have been reviewed by the Bureau ac company all approved devices. Both approval label and instructions should be consulted by the user. Cleaning and Disinfecting Respirators Respirators, particularly .the facepieces, should be scrubbed daily after use with luke warm water and soap. This not only is good hygienic practice but also prolongs toe life of the rubber, as otherwise the dirt, oil, aid perspiration from the face may cause rapid deterioration. Respirators should also be dis infected at regular intervals. If a respirator is worn by toe same person, disinfection once a week probably should be satisfactory in most instances, depending on conditions of use and thoroughness of deansing with soap and water. A respirator that has been worn once should be disinfected before it is given to another person to wear. There are several procedures for disin fecting respirators; however, as certain res pirator parts may be damaged by toe disin fecting agent; toe manufacturer should be consulted as to the best procedure for his device. This warning is particularly pertinent at present, when-toe use of substitute mate rials is so common. Common disinfecting procedures indude scrubbing or immersing toe: respirator for 10 minutes in 70 per cent alcohol, two per cent CTCsd) or a Solution of formalin made by mixing one part of 40 per ,cent fonnalde-.. byde in nine parts of wateri When such agents as cresols are employed as disinfect ants, the parts that come in contact with toe n 31st National Safety Congress skin should be rinsed thoroughly with water, le, it should be stored properly. as some persons are highly -sensitive to such materials. A good procedure is to- have a central place of storage, possibly with sub-stations Cleaning and disinfecting afford an oppor at strategic points if die plant is large. Stor tunity for cleaning or replacing filters, in age should be in essentially dustproof con specting valves, headbands, facepieces, and tainers away-from- sunlight and in a cool metal parts' that might be distorted. place (not near radiators or steam pipes). Small devices, such as dust or chemical Maintenance and Storage cartridge respirators, can be-kept in paper or cellqpbane bags. These derices may be A most important phase of any control , -numbered and assigned to some me- person, procedure is maintenance. Ounce of proper who returns diem at the end of the shift equipment and adequate instruction are com to die central station for cleaning and re pleted projects, but maintenance is'-a con placement of filter dements, and for repairs tinuous problem requiring constant atten if necessary. Thus, wearers areassured dean tion. As such it should be supervised by devices in good working order for each day's someone thoroughly familiar with die appar- f"fee. This program may he facilitated, by as atus bring used. signing two respirators to each person, one bang used while die other is being serviced. Washing and disinfecting die device af fords an opportunity to inspect it for minor Larger devices, such as gas masks" and repairs. In 'addition, it should be inspected hose masks, psuUy^cxwie^eguipped with thoroughly at monthly *or laager intervals, sturdy case dr -trunk -that can serve as^a depending on die apparatus, conditions of storage place. If thej^ace^stored at strut use, and storage. Devices for emergency pur points for emergency user'theyymight poses should be inspected after each use to placed in a case with a glass window that assure that they will be in good condition requires breaking of a seal to assure that and immediately available if an emergency they have ngt been used or tampered -with. arises. After die equipment has been cleaned The seal should'bear* die date of toe last and inspected and any necessary repairs inspection. L/ Prim f. \ At Hagt* that 1 comm equdvc of a'd In. days broke r