Document 06xy17d67e7jO1nXKRdryNOQk

3 5T H4 NATION A L S A F E T Y CONGRESS :.v^' 7*>. : . VOLUME V AUTOMOTIVE AND MACHINE SHOP SECTION -* ^t`\ jj,*'*'.y.-.r.'-. A^illOpAt SAFETY OkH^sWACK ER B RI V E fri-Wf-fts/yi-fo <.w;~ >>v. . v COU llii - CH IC AGO 6V ItX. v . : e ' - ,v *. T-: o .> Automotive and Machine Shop Section Executive Committee 1947-1948 General Chairman---J. E. MOORE, Director of Safety, Corporate Service Incorported, Detroit, : Midi. '. ^ /' Vice-Chairman--L.B. LOOMIS, Safety Engineer. Fisher Body--Ternstedt Division, General Motors Corporation, Detroit, Mich. 1 C. A.. DeMONGE. Safety Director, Kdscy-Haycs.'Wheel Company, Detroit; Mich. Secretary--D. L. McCULLY, Safety Supervisor, Westinghouse Air Brake Company, Wilmerding. Pa. u Program CommUtee Chairman: CEO. F, NUERNBERGER, Safety Engineer, A. B.. Dick Company, Chicago, IlL^ R. D. HARVEY, Safety Engineer,/F^e Murray Corporation of America, Detroit, Michigan C,. O. ENOCHS, Safety Director, fehevrolct Flint Division of General Motors Corporation, Flint, Michigan 1. F. H. HUMPHRIES, Manager Safety and Claims Division. American Car and Foundry Company, New York, N. Y. . - .1. '* Engineering Commits Chairman: F. W. FI3KE. Safety Director, The Brcvrer Titchncr Corporation, Cortland, New Ydrki . r-> BARNEY J.'POVOLNY, Safety Director, Detroit. Diesel Engine Division, General Motors ; 'Corporation,Detroit, Midiigan WM. SMITH, Director of Safety. Ford Motor Company of Dearborn, Michigan ' Membership Commit!** Chairman; PAUL J. BLACK. Safety Supervisor, Westinghouse Electric! Corporation, Lima, Ohio ARTHUR E. EWING, Latxobe Electric Steel Company. Latrobe, Pa. FRED G. YELTON, Safety Director, DclootRany Division, General . Motors Corporation. Anderson; Indiana Nows Letter Committee* Chairman: PAUL F. BUNGER. Safety Director, Frigidaire Division. General Motors Cor- pornioo, Dayton, Ohio LOUIS A. GALANTUCCI, Safety Engineer, General Electric Company, Bloomfield. N. J. G. W. YEMM, Safety Director, Otis Elevator Company, Harrison, N. J. Hocdfh Committee Chairman:. A: L. BROOKS, MJ)^ Medical Division, Fisher Body Division, General Motors Vv'.Corpbratioa, Detroit,-Michigan ' > CL R ENGEL, MD, Assistant Medical Director, Westinghouse Electric Corporation. East y FRANK A. PATTY, Dire&r ^ofc Industrial Hygiene, Ccneral Motors Corporatioo. De. trait. Michigan *": ' 5 35th Ndtional-S&fety Congress, 1947 ^ . '^jPubfidtr Committee Chairman: O. C. BOILEAUrSupermor of Safety, Health and Retirement, RjCA, 'Victor Cor poration of America, Camden, N. J. v- GERALD C. SQUEER. Assistant Director of Personnel, Bulldog Electric Products, Detroit, Michigan ! ')' ' "" ________ *' - ' . EDWARD G. HOLTZMAN, Director of Safety and Medical. Departments, Wagner Electric Corporation, St. Louis, Missouri Statistical Commlttso Chairman: H. J. JENNINGS, Safety Engineer, General Electric Company, West Lynn, Massa chusetts V W. E. BROWN, JR,, Safety Director, The City Auto Stamping Company, Toledo. Ohio' LOYLE DAVIS, Director of Personnel and Industrial Relations, Mueller Company, De catur. Illinois s' Ofrfh*-Job Cocnnttte* ` Chairman: M. P. BIANCARDI, Safety Engineer; Health and Safety Department. Industrial Relations, Dir., Allis Chalmers Company, Milwaukee, Wis.1 ROBERT C. BENSON, Director of Personnel and Safety, Laming Stamping Company. Lansing, Michigan . . ) E, CLARK WOODWARD, Director of Safety, A-O Smith Corporation,. Milwaukee, Wis consin Poster.CommUte* Chairman: CARL PETERSON, Safety Supervisor, Plymouth Motors Division of Chrysler Corporation, Detroit. Michigan CARLTON R, REID, Safety Engineer, Westingbousc Electric *and Manufacturing Com pany, Springfield, Massachusetts HAROLD M. ERICSSON, Director of Safety, Nash Motors. Kcno Members-at-Large--*]. W. YOUNG, International Harvester Co, Chicago, HL;#0. F. LEH-. MAN, Chrysler Cotp, Detroit. Mldu *W. A* BECHILI, Chrysler Gorp, Detroit, Mkh.; J. C. BOWER, toat Mifflin Art, Pittsburgh. Pa^ *M.'A. CLABX 5537 Devonshire Rood.. Grossc Pointe, Mkh.; *H. B, DUFFUS, Wetttogbouse IU<xlricCor^ Pa^ HOYT L. FRACHER, Detroit Steel Products Co^ Detxoit, Mldi4 ^G. A.^UECraNMEISTER, Dominion Forge fc Stamping Co^ WalkerTffle.' OnU Canada,! CARTHY, Fisher Body Detroit Dir,, General Motors Corp^ Detroit. MIch4 koBER.T SHAW, Detroit Diesel Engine Dir, General Motors Corp. Detroit, Mkh4 LT. OOMDFw. PAUL S. STRECKER; *R- F.THALNER, Bukk Motor Dir,' General'; Mott^Xiospi Flint, Mich.; *V. I. TROTTER: *C. E. WOOLIEVER, A- O.'Sndth G^ Wis. ' ' '* : r-:' ; Staff Representative--ARTHUR S. KELLY, National Safety Council,, Chicago, IILV'-` s Indicates Past General Chairman * ' Automotive and'Machine Shop-Section 7 ) MONDAY AFTERNOON SESSION October 6, 1947 Presiding: D*. A. L.-Brooks. Medial Director, Fisher Body Division, General Motors Cor poration Recognition and Control of Fume and Dust Exposure By V. J. CASTROP Research Laboratories Division, General Motors Corporation Illness which can be attributed to the oc accepted opinion as.to their effect on health. cupation may occur in the automotive and Many conditions are corrected or . improved allied industries. While/'oteripational disease because of reasons other than their effect cases are: much fewer id tlumbcr than those upon the health of the employees. Better resulting from accidental injury,' there stilt remains tlje need for vigilance in maintaining products, better employee relationship, reduc * tion in maintenance of equipment may be a healthful working environment. `The re cited as justifiation for management's de sponsibility for employee health is delegated cisions for such correction or improvement. by. management to the medical director with Generally speaking there' are two means of the safety director charged with matters per entrance of toxic compounds into the human taining to safety. For the smooth-functioning body under industrial conditions, namely, by " i either department It is necessary that these Ingestion or via-the respiratory tract through .vdividuals' work in dose harmony with each the inhalation of fumes, dusts, mists or gases, other;" ingestion is of importance if toxic materials A safety engineer who is capable of recog which have a systemic effect are used and , nixing conditions which may be detrimental adequate' washing fadlities are not provided, r to the health of the employee is an excdletiu.. or, where the employees are slovenly In 'tbdr teammate for the doctor in any employee ) personal . habits. Inhalation 'is considered the health maintenance program. The safety cm' most important portal of entry of fumes gineer. need not be capable of actually sam- or dusts and the partide sire, therefore, bc- pUng air in the environment or designing a comes significant in evaluating an exposure.. ventilation , system Tor the control of toxic The particles which cause the physiological materials. He? should, however, have know`l changes are those which are small enough to ^ edge of the materials which have been proved remain suspended in the air and not those harmful, should be fairly wdl informed of which immediately fall to the floor. Flying bow these materials may be used safely, have partides, which*are of concern to a safety some understanding of basic control measures man and for which he advocates the use of which are normally recommended when such . goggles, are npt of hygienic ilgnificsnce sine: materials arc used. The Intention Is not to present a (highly technical discussion of fume and dust ex posures' or detailed information regarding ventilation systems, - as such matters are of interest-to theprofessional industrial hygien ists and of comparatively little value to safety they are not of respirable slxe. To Judge the seriousness of an exposure by the quantity of detritus adjacent to 'an operation' is .often misleading. This is especially true where tnechanlral ventilation has been, provided which will remove the ffine^matcrial but Is inadequate to liSpA orV.$opWy the larger engineers. This discussion will .be limited to the- mbse.; basic prindples of * Industrial hy giene-** they relate to fume and dust ex*paeures/ to ; Indiate what, control measures arc:* available or- used' to . protect -the an- ployeeV health, and. to call: to your attention operations and. materials which arc commonly used,in,the automotive,and. allied industries, at. tbcVsame.' time.,: indirating the generally. particles. ` .* *` ' In. evaluating a|t^xposure It h necessary to consider.the toxidty of the material, die duration of the exposurevtbc average concen tration of the contaminant, with spcd&l atten tion bdng paid fo/tbore;:operatiots:whkh produce high concentrations at tome phase of an operating crd^amktbe 'measures which hare been provided TO-control the exposure. 8 35th National Safety Congress, 1947 Medical record* of the individual* subjecdxl ` considerable-period. There remains much to to the exposure may be of value if the exami be learned regarding the toxidty of many nations are. thorough and frequent and not substances used.in Industry, anditb hoped of a cursory type. It must be remembered that with more research and study that the that oecupatiotud diseases are slow in develop answers will be found. ment and in some instances lasting in effect. So much for the general picture. Now let's Slow changes may not be detected and the take i look a^.aome specific operations.? mere fact that cases have not occurred b no definite assurance that exposures to known toxic materials may be ignored. The determination of the concentration of the toxic material in the air is important In evaluating the exposure. Tests of this type are not only indicative of the degree of con tamination but in some instances which op eration is the major offender. The apparatus used in collecting the con taminant and the method used in estimating the amount present in the atmosphere vary with the type of material. Tests of this type are specialized in nature and are beset with many pitfalls which can lead to very errone ous results and conclusions if done by other than experienced personnel. In a discussion pertaining to toxic ma terials it is generally Decenary to quote per missible concentrations or as it' b sometimes expressed -- maximum allowable concentra tions--permissible limits, or threshold limits. These terms are used extensively by industrial hygienists to indicate concentrations of a substance in. the air which are considered compatible with good health. The limit usu ally applies to exposures of eight hours dura tion (or m prolonged period. - The limits are; for the most part, advisory standards or] bench marks which 'are prac tical to meet. In general, these limits are de rived from three types of evidence all of which have value and limitations. Welding--Welding processes most common ly used can be divided info three types, arc. gas. and resistance. The safety'measures per taining to dbthing. goggles, and hdmets are of common knowledge and- therefore^ shall not be considered in this dbcuadoo. \ Arc welding when-performed on uncoated steel does not produce a condition whiCh is considered harmful to the welder provided it b accomplished l^a-fomporatiyely large open area. The fumes \whJkh result from, welding consist essentially xrfr the .oxides of iron and oxides of metals which may comprise the steel or coating of the welding rod. Some in vestigators have found characteristic mariings oo^cbcst x-rays of men who have, welded under pevvbtc conditions for long: periods of time. These markings are presumably due to* the deposition of iron fumes within the. lungs, but it has Dot been demonstrated that sudi fumes have caused physical impairment. A frequently suggested limit, for welding fume b 15 milligrams of iron oxide per cubic meter of air. Concentrations of tilts magnitude existing in the .workroom would materially reduce visibility and thereby become a nui sance or an unsafe cooditioo requiring cor rection. Welding .Within "confinal areas such as tanks, inside machinery or equipment, or in small room*, presents* a condition which can be of concern. The concentration of farce is materially higher under these conditions as i. Animals have been expoeed at different there b little opportunity far-dfludon- by concentrations and the effects noted. natural air. aments normaHy pterent ln a x. A few experiments have been made large shop. Nitrogen oxides., formed by ..the on human subjects for short periods of ' electric arc when, inhaled -in sufficient*- quan time. tities causes fluids fo form in the lung-edema 3. Safe limits have been arrived (at by measuring the concentrations of sub stance in the workroom air and corre lating . this information with -remits of medical examinations of' Workmen./ > . There U no magic' connected witlr'these limits and the mere - fact that they are [ex ceeded does not necessarily, mean that, some --with thejesoltant.failnre of the respiratory system.; While wddh$-in Jatgciopcnrareas these toxic-gases are normally, not.present In sufficient quantities.to cause harmful effect*. However,-when welding b.done In confined areas; the nitrogenoxides may.reach*;con centration which will .be harmful^-;' ^ Ga* welding gtmerany b nce. produciire^oi one will definitely become fll/Wt there b a good probability that someone will suffer ill effects if the limit is gready exceeded for a harmful fumes..There are. boircvay- in beat* ing two potentially-bafinful dcpocures.'Whlfc boric add or borites- generally-are used in . . w* * ^ Au,tomotive and Mat'bine < Sliop-Section ,: , ' 9 brazing fluxes, some metals require fluxes disepmfort'-ausodated with metal fume fever conadning* significant quantities of fluoride may remit from such an exposure. Compounds and fumes from these fluxes have been known to produce, significant nasal irri tation, Fluorides In general'are looked upon with suspicion since theupay. produce harm* ful effects, upon the ^ora^structure. A limit of a.5 mg. per cubic n^tojtas been suggested for fluorides; but no . standard has been agreed upon. Most industrial. hygienists at tempt to keep them as km as practicable in order to be absolutely certain that bone dam* age does' not occur among the workers. Where warranted 'the control of welding fumes is generally accomplished by providing a mechanical ventilation system. The type of ventilation used is dependent upon the na ture of the welding. When the object to be welded is positioned in a fixture or jig it is possible to obtain effective. control of the fumes by the use ofra, grill side hood, or flexible duct near. the. tburoc of fume. If the pans, are large and it Is necessary to weld more than a foot from a fixed point It is Silver solder Is one of the more common difficult to obtain good control.of the fume alloys used in fanning. Solders of this type with reasonable air- volumes through sys vary, in composition .-and may in some in tem using flexible ducts. Since the effective stances ^contain cadmium which if volatilized range of most flexible ducts is approximately in sufficient quantities is considered to be 8 inches from the duct opening, it is neces harmful. At present the suggested limit for sary for the welder to move the duct when cadmium fume in air is r milligram per 10 ever the arc is outside this range. prac cubic meters of air. tical result is that most , ducts arc\nqrmally Resistance, spot, or butt welding of plain not moved any!''the ventilation system does steel;is of no concern from the physiological not remove the fumes -when liberated. Ac standpoint. The fumes arising from such . cording to reports this type of system has operations generally ate caused by the vola been effectively used in shipyards, for the: tilised- oil which, has come upon the metal - control of welding fumes in confined areas. itock. during previous operations or which In vieW of this experience it should there has been placedupon the metal as a rust fore be a satisfactory means of control few preventive. welding fumes in tanks; However, excellent The preceding dftcmskm of welding opera supervision and education is necessary to tions' has been based upon the. assumption make such systems effective. that the metals being welded are of plain Where the room volume per welder is large, steel. The performance of welding operations, the natural ventilation within the plant is either arc; , gas, or resistance, upon metals usually sufficient to prevent the.accumula which have been* coated with such toxic- ma- ' tion of excessive concentration of fumes from teriab as lotd, cadmium, or mercury may plain steel welding. Circulating fans directed cause harmful exposures. The beat crT-the from the side help to dilute the fume Which flame or of'the arc causes vobifllation^lof may be concentrated in the'breathing rone of there metals. Welding or cutting of terne-jvthc welder.V.y plate'ox.other metals containing significant ^ .: Another tbcafas of control, is the use of per- quandtfcsof lead can remit in the rolatiliza- renal respiratory equipment. Air litre respira donofkadfiuhe, which if inhaled ,for a tors and fume respirators have been developed suffideni'period of rime, may-'result in lead which will provide adequate protection. Some absorption and ultimate poisoning. The cut* manufacturers of this type of equipment have ring or welding of surfaces which have been on the market welders* helmets with facilities coated with paint containing lead has caused for providing fresh sir to the wearer..Tbcjuse lead'pohdningjn.tbe past and will continue of this type of equipment has .bcca Ufltit&L to >do wonte adequately ooottoHcd. Since the welder Is already burdened with Welding of cadmium plated material was helmet, goggles, and. protective dothing -he ' attributed -as the cause of . illness and even probably will not be receptive to a respirator. -death to a number of individuals during the It is usually, sufficient -in most welding for. recent',war activity. The reported cases in the employee to wear an ocdlnary helmet and dicated- that.dcath.occurred in a compara-. -to arrange, the position.of the work so as to tivdy short time after the exposure. prevent the concentrated fume from Bowing -*>Welding LOf galvanized metal- causes the under the helmet. . . . volat filiation of the zinc coating. Temporary Dry Grinding--The dust resulting from the 10 35th National Safety Congress, 1947 grinding of nontoxic metals which arc free of Machining--Smoke from oily parts is the sand U generally considered a nuisance and prevailing source of air contamination at is. not harmful per sc. Despite this tact tome machining operations. \T11pm has not been tUte laws require griding operations to be attributed to this type 6f exposure. As U the ventilated. This requirement has probably case with most- fumes and dusts of the nui been a bold over from the days when sand sance variety little Is known as to what ef stone wheels were prevalent and also to pre fect, such materials have on already- existing vent the creation of a nuisance condition. physical abnormalities. Grinding wheels in use in industry have ar Machining operations on steel produce tificial abrasives such as aluminum oxide or Urge chips-or turnings; consequently, dust ` silicon carbide. Emery, which is a natural is not a j^objem. Operations involving the product cotnpoecd of essentially aluminum machining of high lead alloys have been and the magnetic oxide of iron, may also be studied, and significant quantities of air- ^ used.- A permissible limit of 50 million par- borne .lead have not been demonstrated. tides per cubic foot of air for aluminum `Graphite which becomes airborne during oxide and silicon carbide was recently ac the machining of cast-iron is not considered cepted bjrtbc members of the American Con to be physiologically significant, and there ferencef of Governmental Industrial Hygien fore is classified as a nuisance dust. Frequent ists. Such a limit is liberal and concentrations ly management considers it advisable to pro of suchNsaagnltude arc normally not en vide ventilation for the machines which are countered. productive of the most dust, as graphite on . When lead, silica, or some similar toxic the clothing and person and surrounding material comes in contact with the grinding madpnery is conducive to many complaints. wheel the exposure to the abrasive matter Ventilation systems' for the maduning; drill may be ignored and the exposure evaluated ing; and so*" forth, of cast iron should in on the basis of the toxic material. If this clude hoods located as near the cutters -or latter material is controlled the nuisance will drills as is practicable. Many of these hoods also be eliminated. ... are in use on production, machinery and are Ventilation systems for grinding /rheeis doing an excellent job of dust control. ^ have been fairly well standardized'and gen Abrasive Cleaning--Since silica is recog erally are satisfactory to prevent a nuisance. nized as the most harmful of mineral, dusts, Hoods should enclose the wheel as completely an adequate ventilation system is normally as is practicable. Air volumes should be pro provided at' the time of installation of com vided which are suffitient to cause an inward mercially built sand blast equipment. Con flow into the hood when using the smallest tinuous usage and lack of maintenance result wheel. This is especially true where toxic in a breakdown of adequate control. Visible materials are Involved. escape of dust is the bat evidence that this Wet Grinding--Baffles, hoods, and guards has occurred and it is advisable to correct are generally located near wet grinding such a condition witbout< undue delay... wheels to prevent dispersion, of the liquid Employees who are stationed in blast rooms used as a coolant. These devices jt'ir usually are dependent, upon* personal respiratory sufficient to control the dust if it4s' nontoxic. equipment. It is of utmost importance that in nature. If the dust liberated is toxic, me such devices are of a type which will provide chanical exhaust ventilation may be required.' the necessary protection. Devices of this type- Buffing and ' polishing--'The buffing com-'1 pound applied to wheels used' for buffing and polishing vary in composition. Waxes and various types of-abrasive are the major components. These materials plus lint and fibers from the wheel are the essential in gredients of the airborne dust. The toxidty are of the supplied-air variety, and it is neces sary that the air provided be free of harmful contaminants. The air compressors should be. located in an area free of contamination otherwise the contaminant will be transmitted to the helmet and the breathing;, zone of the worker. * . >~ ; * t is- dependent upon the type of abrasive. Normally, ventilation within the. room-b Generally ventilation is 'provided so as to `provided so as to Improve visibility and to improve housekeeping and reduce the num help prevent the escape of duk. to the sur^ ber of complaints and not ' because of the rounding areas not'to reduce the concentra hazard to health. tion of silica dust to a. safe level. Automotive and Machine Shop Section 11 Turablast or routing table type of sand Practically all industrial plants have opera - blast units should be provided with sufficient tions which involve the use1 of leading base entllatlon to prevent the escape of silica bearing metal ' or solder. Babbitt baring dust. Leakage due to excessive'wear should metal containing, approximately 75 per cent be remedied. lad has been encountered. The composi Small sand blast Cabinets, where the opera* tion jot solder metal '-is variable and de tor controls the blast nozzles from outside the< pendentupon the purpose Cor which it is cabinet, frequently have faulty seals around used, with ordinary soft solder containing a the door* or the rubber! gauntlets are loose comparatively high percentage of lead-,- . or tom. The dust which escapes from the . cabinet through these openings is in close proximity to the breathing zone of the em ployee and in many instances exceeds the per missible limit for silica. This leakage should Assuming that the babbitt or* solder \n use is one containing a significant amounrof lead, the question then arises as to whether or not the employees working with this ma terial will become UL The answer to such a be corrected anid>th'e men.should not be re question could be given by z qualified in quired to use respirators. dustrial hygienist after he had seen the opera If the articles being blasted are free of tion and considered such factors as the tem silica or other toxic material, the dust result perature to which the metal is hated, the ing from grit or shot blasting is classified in method of removing excess solder, the length the nuisance category. It follows that the of exposure, and the effectiveness of the con maintenance of ventilating systems for grit trol measures provided. blasting, although desirable, is not always It is a well known fact that' lad causes so necessary as for sand blasting. illness if absorbed in excessive amounts, and The use of steel gi>t or shot in blasting therefore operations wherein lad . is mod rooms produce -excessively high ooncentra- have received considerable * attention and ->ra of dust within the enclosure. It is there- study^Odt of this experience certain prac >re, necessary-to-protect the worker,vtitbin tices are knbwn to produce excessive exposure the room. 'The'iemarks included in.sthe Sec wheieas''t>ther. practices have been proved not tion devoted to sand blasting rooms artNhere- to be harmful: It. is generally conceded that fore; pertinent when considering rooms in excessive concentrations do not result from which steel grit of shot are used as the abra operations where solder is applied by mans sive. of an electric soldering iron. This is probably Vapor blasting, a variation of sand blasting, due to the small amounts of solder used and is bf comparatively recent development. This the comparatively km bat of the metal. procedure Involves-the use of fine silica and When an iron is/used which is-bated In a water under pressure. The silica used in vapor small gas fired furnace, the exposure may be blast units varies in size and may even be as of grater consequence. Solder which remains small as 1250 mesh (approximately to mi on the iron coming into contact with the crons). It Is generally believed that airborne flame or bat 1 vulnerable -for volatfliguioa. silica partidcs bclow 5 microns axe most rig* Small amounts of solder drop from the iron niScant in causing silicons. It then follows onto the hot Boor pf the furnace where it is that operations involving the use of silica readily volatilized or oxidized. The oxidized .-abrasive wjyosc initial partide size approached' 'material may become airborne due to dis that order of magnitude are more hazardous,' turbances crated by the flame or by remov and require continual vigilance in maintain ing or placing' the soldering iron In the fur ing good control. It is, therefore, essential that nace. Frequently industrial hygienists recom the vapor blast cabinets be maintained so mend that ventilation be provided for bating that leakage of mist' docs not occur. Good units of this-type .thereby' removing lad housekeeping is also essentia] as spillage of fumes and dust from the environment. This the. sand and water sludge upon the floor is particularly , true in small rooms or where '~^pl create a . source for .dust dissemination many units are in use. ien - the. water evaporates. likewise, con The atmospheric contamination occariobcd tainer* of the dried sludge should not be al by the use of either'gas or electrically hated lowed to *tand fn the factory vjhcre they pots containing solder is dependent on a can be Influenced by air currer/tv of high number of factors. With higher temperatures vdodty. more volatilization will occur and the rmirr 12 35th Motional Safety Congress, 1947 will be the exposure. With the higher lera- Heat Treating-High temperatures 'are a perature the metal ii more readily oxidized to ' frequent source of complaint from employees produce a dross consisting of a high percent- in heat treat departments but such condi- age of lead oxide. The dross may provide a dons and thdr control are not within the protective coating to reduce the volatilization subject matter. under discussion, of the lead; however, disturbance of this coat ing will create art exposure. As a safeguard against excessive contamination, pots contain ing soldo' or babbitt-are usually ventilated.' Wherever possible it is advisable to enclose the pot as completely as possible and provide sufficient air volume to overcome the thermal ctfccu of the molten metal. Attempts have been made to use natural draft ventilation systems to control (hoc fumes and In those instances where the ducts were not of suffi Fumes disseminated from cyanide pots are often associated, with cyanides used as fumi gants or as the lethal agent in death cham bers and supervision as well as rtve employee becomes apprehensive. Fumes from such a source arc irritating and because of (his property should be adequately vdfttilatcd. The Irritant nature of the fume is caused by alkali formed upon decomposition of the cyanide. cient diameter the system was inadequate Molten lead is sometimes used as a harden A preferable method is the use of mechanical ing medium for metals. Frequently charcoal systems^ or some similar- material..!! placed on 'the Thc/removil\of excess soldo with power surface.of'the metal to conserve beat and driven Stools, such as grinding wheels, discs, prevent oxidation. A covering of this type or wire Wheels/creates airborne dust. which reduces the volatilization of lead while the may contaminate large areas of the factory bath Is quiescent, but has no effect,whik the if the operation is extensive. Diligent use of bath Is In use.. Adequate ventQsition should abrasive cloth will also result in excessive therefore be provided for baths of this type. concentrations of lead dust. Filing, however, As complete an enclosure as Is practical for is not productive of small particles and is the operation being performed is advisable preferred over the use of power driven tools. (with air quantities dependent upon Use open If filing is not practicable or feasible it will areas in the bood. To prevent contamination be necessary to provide some type of me resulting from volatillntloo of lead accumu- chanical ventilation system for the solder re - taring in tbc combustion chambers the prod moval operations involving the use of power ucts of combustion from gas fined lead pots tools. Since the permissible limit generally should be vented to tbc outdoors and not accepted for lead is- i. milligrams . be allowed to dhslpate Into'fhe wctfcrooes. cubic meters of air (555' cubic feet) it necessary to* have an effective system ~\Ircm Foundries--The principal Ingredients oFfoundry dusts are sQicx, tea coed, days, usd vide adcquaic co-rol Engines exptri^ parting ompdao*. He pmkeoimnt: B- m designing ventibuon sjttem. U> nIV_SaI`lrin bTdqSdeat ^on^rtdeTpW toxic materials shouIld be consulted, otherwise a costly system might be erected and later discovered to bcentirdy ineffective. Fre quently solder removal operations require tbc use of portable tools on large objects and a o,f the.f*o_u__n_dry operation is-bring studkd and what operation bbdhg performed...Tbc control of dust'b tbc major problem, whereas fume b of secondary importance.- ' local exhaust system would not be effectfve. as ' A discussion of alt tbc aspects of tbc in-, is the case in tbc fabrication of automobile dustrial hygiene problems, injsuch,,plants bodies. General contamination of. the'factory > would-require a separate treatise.. For.' _w.JithL le__adJ dJ_u_s_nt h_a__s_b_e__e_n_-Ie*l_i_m_!in__a_t.e__d1 b1_y__._c_n__dfo_s_______p_r_e__s.e__n-t-----d--i-s--c--u---s--s*i1o.n it .s1h__o_uUld iWJ suf ing the entire operation in a large booth and state that all obvious sources. of-dc exhausting a sufficient quantity of air from penion should be reduced to a minimi the enclosure to insure a constant inward vadcq^atcV localized. exhaust vsystemv- In\- a Bow of air from the factory into the. booth. mechanized foundry such places.wodld.be Under these circumstances no practical sand conditioning and" mixing equipment, amount of air;acould be removed.from the tumbling mills, shakeouts, coifc removal arid booth to reduce the lead concentration to a knockout stations, -.' transfer' piihits- of .`-dry safe level, and .'therefore'it b necessary that sand, `abrasive'blasting operations, and;all the men. working, therein be provided with ^grinding ^operations' pet fanned "00 .castings adequate personal protective devices.- containing appreciable quantities of sand. - Automotive and Machine Shop Section 13 Maintenance of ventilation equipment Is a major Item in foundries became of the abrasive action of.the dust* Tt is imperative that a good program be maintained so as to keep the equipment functioning at maximum effidenqr. Because of the heat associated with large scale foundry activities it is a common tight to see pedestal Cans or air cooling ducts dl- rected inVtuch a manner as to create crow drafts which interfere with the efficient re* moral of the jdust diipotion. Better discre tion in the placement of these fans or ducts will go Car In'reducing dmt concentrations in the areas Where they are used. After the obvious has been corrected, it Is advisable that; a survey of the foundry be made by an industrial hygienist so that an accurate evaluation of tbe exposure may-be obtained. iq " `v__ ) Respiratory \Protecime Devices -- As has been stated, the atmospheric concentration of dust and fame and other materials may be reduced to a safe level by adequate ex haust ventilation. In some cases it is possible !o correct the* condition by substituting a less toxic material. If these, measures are not practical. respiratory protective devices may be- used. They^may abo prove valuable in giving protection during-an emergency or to provide protection for intermittent exposures or to supplement otber~metbods of control. They: should, hbwevefc'ubt-'he considered as tbe desirable means df^gmtroiHng a health hazard. Experience has shown that frequently pro tective devices have been Issued which do not provide adequate protection. Upon inquiry information was generally offend that the safety engineer was hot too well Informed as to what should have been provided. . TheJU^S. Bureau of Mines at tbeir experi mental station in.Pittsburgh tests equipment of thik-type and studies the jMqjUm^offered to the wearer. If tlwtl2^qiOrmtl*fai;>^ tory. in performance. thcy^Utue an^pproyil number to the tnanufactum\whljh appear^ on the device as well at thc''TXmtalner in'which it Is received from the manufacturers. The approval granted by the Bureau also stipulates that type of materials for which, it is approved. It has become general practice In the field of industrial hygiene to recommend the use of only those respirators which have been ap proved by the Bureau. Safety . engineera should likewise insist.that -such devices be procured and acquaint themselves with the type of. protection afforded by cadi device, and thereby provide adequate control foe the individual,-wearing the equipment. Some en gineers prefer to stock only that type of res pirator .which will protect against the more harmful dusts Or, fumes, since a respirator of this type will also give adequate protection for materials of.lower toxicity. The advan tage of such a procedure has merit as it re. daces the types of devices needed in Rod; and likewise insures the correct device for the more serious exposures. Metal Cleaning By THOMAS MOONEY Med-Fac Industrial. Hygiene* laboratories Thc compfcte finishing of metals by eketropiatlngmay;indode: i;?Cloming by ahrati^ a.\Polishing the base i x 5. C3c*ning with solvents. 4.j Cleaning with alkaline solutions. '.'5;Cleaning withadds, often referred to as VTiiABngrv'. : fi.\ Metal-deposition or electroplating. Buffing the deposits.s 8.': L*cquering the' finished product. In abrasive'cleaning. sand or Red shot is ' used under pressure.jTbc potential health hazards in this type ofoeaning ate exposure to dust of a high free sQSca. (SIO0content caused by the sand andaho to metallic dusts whererroetal* capable ; of producing :toxic dusts are deaned by sbot 'and sand blasting. Steel shot biasing ba mud* less severe health hazard than sand blasting: consequently, Red shot abrasive doming methods should be used wherever possible, v - : ' The ' maximum; allowable concentrations (Mj\.C.) for free silica are five million parti- Automotive and Machine Shop 17 scratches, before the petal is platted or paint- the area; All workers involved in metal fin ctL Tbe principal hazards to health in metal ishing where lead Is used and ground with ) finishing are the dusts of toxic metals such power .tools -should be. required to wear a as lead, whlch^are used to fill hollow sur- metal fume respirator approved by the U. S. {aces when pbwhr grinding or disc machines Bureatr of Mines for lead dust, if the con are need to grind'them down to a .smooth centration of lead in the air is. 1.5 milligrams finish, as is often done in automobile fin per. ten cubic meters of air as determined ' ishing. . . by test. The writer knows of do lead hazard! In operations of this kind, where the lead introduced when. finishing lead surfaces by surface is ground with power tools, the job hand filing.. shoald' be isolated from other adjoining de-f ' REFERENCES partmems and hare suction applied to it to l. BloOStSeW." J. J., and Blom, Wm., "Health remove the fine lead particulate dusts from . Hazards, In Chromium PUtin*.'* Public Health Re^ port*, 4J;;*23jO (192*). Control of Solvent Exposures ' By E. C. BARNES Industrial Hygiene Engineer ' Westinghouse Electric Corporation The term "solvent** as used in industry mixtures are supplied to industry; In addi denote?]* variety of liquids that are used tion to this group of liquids which is avail mainlyrfbr tbc purpose of dicolving tome able to industry in large quantities, there other material. The term is used rather loose are several thousand others which are avail ly and may indude such'liquids as water or able in quanthjpof a few -quarts or gallons. adds.; Although these are many; interesting Out of the'/miBv millions bf)gallons in floors involved in the proper control of all volved, tbc N*pp-~tngank solvcntY which are types of solvents, perhaps the greatest con available In Urge quantitia present the cern is attached to the organic tolvenuTand greatest' problem of control.. At the same this discussion will be limited to. that group time, this group- of solvents has been used of solvents generally referred to as "organic and studied sufficiently, so that reasonably solvents." Most of these solvents are pur good technical. information and methods of chased to perform a sped&c function and. control .are available.`Many-of the several they`are later thrown away, usually'in the thousand organic solvents used in small quan form of a vapor. For example, a varnish may tities axe not so-well known and adequate be made by dissolving a min in toluol. The technical Information may not always be varnish 'Is applied to some piece of equip available. They thus present a more diffi ment and-tbe toluol is 'then evaporated by cult problem in control. placing the equipment In an oven. Or, per In addition to these solvents which are*', haps it la desired to wash grease from mate now available,, there; are.probably at least metal ports. _The parts may be wet with the a doxen new organic solvents made, available solvent until the grease, ia removed and they in large quantities each year, and hundreds are theq allowed to dry. We'can almost gen of new searchts are made available In limited. eralize-and say that solvents are purchased quahtitieY'-A continual check 00 new nuiV for th* express purpose of creating solvent rials and new processes is therefore advis vapors.'These! vapocs create hazards which, able to be certain that the' toeYdf new solv-. most' be'Controlled. ents will be adequately controlled. There are''about soo different organic When we speak .of controlling solvent ex solventa availablc In dram or tank'car quan posures,' yrt obviously- must Ihdude all the ,, tities. These solvents arc supplied to industry hazards associated with the use of the solv botH..a* a;.specific-chemical `compound and ent. We must-Indude'such dements as. fire, aho.i-ak-a* mixture'of ooc- or more of these explosion, and bcalth hazaixL When speaking ebemkal; compounds. Thousands of these of control, we; may ' ted 1 the' desirability of 18 35th National Safety Congress, 1947 establishing tome kind of an automatic con- indicates whether the vapor is lighter or trol which would shut off or reduce the ex heavier- than air, and in cases where highly posure before hazardous conditions are creat concentrated vapors may fscapc * from en ed. It would be nice if we had a thermostat closures, it. will be known whether these or regulator that would automatically, turn vapors will tend to flow downward, or up off the exposure before any hazard was ward throughtbc air. You will note that 1 created. said "concentrated vapors." J should like to Automatic controls should obviously be emphasize this because there is frequently a applied wherever they are practical. For ex misunderstanding in connection with the In ample, combustible gas alarms may be used terpretation of the flow Of vapors of varying to control the explosion hazard in an oven densities. If there are only a few hundred being used to volatilize solvents. Automatic parts per million of. vapor in air, this mix releases may be installed to actuate fire fight ture will not tend to flow upward or down ing equipment the moment a fire *tarts. Un ward through the air when it is released, but fortunately, we do not have such a gadget will rather be carried along with whatever which can be attached to one of the work air currents may be present at the point ers to indicate when he is over-exposal ,, where it is released. You are all familiar with Other methods of controlling the human the high school chemistry experiment of exposures must be utilized, and these will, pouring carbon dioxide from one beaker into be discussed later. Essentially, control of another beaker containing a burning candle . solvent exposures must be based on preven . and the resultant extinguishment of the tion of hazardous exposures. In order to pre flame on the candle. If the carbon dioxide vent these exposures, certain technical in in the first beaker were diluted to a concen formation must be available. Equipment and tration pf only a few hundred parts per; mil processes must be properly designed. Finally,' lion of caxboin dioxide in air. it would not .quantitative measurements must be made to pour from the first beaker into the second establish the extent of the exposure. Perhaps but would be carried away with any air. cur- we should consider these three elements more reffis and rapidly diffused in the. surrounding carefully. * Before giving much consideration to the design of a piece of processing equipment or a manufacturing operation involving organic air. Thus, any interpretation placed upon vapor density must take into consideration only thoie Vapors which have not been dilut ed appreciably with air or otbex gases. solvents, a considerable amount of technical It is certainly desirable to know whether information must be available,. Such clemeu-. a solvent is flammable or non-flammable. If tary data as the boiling point; vapor; rplres-. the solvent bf noft-flunmabte. no spcdal con sure, vapor density,, fUmmabtlity, flash point, - sideration need be given to the possibility of explosive limits, corrosive action,, and .last: an explosion or the danger qf fire. If the but not least, the Maximum Allowable Con solvcttt is' flammable,. however, spcdal con centration and skin irritation properties must sideration most be tfven to Its use so that be known. the possibility, of ah urtcootrolls! fire or ex The boiling point of a liquid is of-Interest plosion may. not occur. Even though condi because it Indicates the temperature at which tions may be established for use of. the solv 5 Urge quantities of vapor will be given off at ent which minimize the fire or explosion haz ordinary atmospheric pressure. It also serves - ard, it is essential that a suitable type, of as a guide in estimating the volatility of a fire fighting equipment be made available in solvent. .. case some accident should occur which would The vapor pressure of the liquid at room temperature, and also at any processing tem perature, is of importance because it indi cates the possible concentrations, of solvent vapor that might be present under varying conditions. When' the. vapor pressure ; is known, the maximum vapor' concentration cause the solvent to born. Fire ..fighting equipment of a type suitable tor the specific solvent involved should be selected. Assuming that the proper fire fighting equipment has. been provided, it then becomes ncccasaryt to train a. suffident number of persons in' its .proper use. , i- that will be present under saturated condi Assumingthat,we are dealing with,*.flam tions can b<* calculated. ^, mable solvent, its flash point must.be known The vapor density is significant since it to properly evaluate the.means.of protection Automotive and Machine Shop Section 19 % -"Mch u required. The flash point of a flam- >ie liquid is the lowest-liquid, temperature at which enough vapors arc given off to form a flammable mixture of vapor in air imme diately above the liquid surface. If the liquid is above the flash point temperature, a small flame will ignite vapors from the liquid and they will continue to burn. Bdow this tem perature, a small flame passed over the sur face of the liquid will not ignite the vapors. Where a solvent is constantly maintained at a temperature bdow its flash, point, there is not much -chance of it being - ignited by iparks or small flame. If. however, the solvent b at a temperature higher than its flash point, any small spark or flame near the sur face of the liquid will ignite it and the liquid will bum with increasing intensity. Thus, we see that a solvent whose flash point b above room temperature can be used without much danger of fire or explosion wherever the solvent remains at room temperature. If, however, its flash point b below room tem perature, care must betaken to avoid ignitCare must abo_.be taken to avoid the. station of explosive mixtures where thej navh point is lets than room temperature. In general; it can be said that when liquids are maintained at temperatures above their flash point, it is possible that explosive mixtures-of the vapor in air will be formed. c The lower explosive limit of a gas or vapor b that concentration-of vapor in air, below which an explosion cannot occur even though a 'source' of ignition is present. If we are operating an oven under conditions where explosive concentrations of solvents are pres ent*, then it requires only a spark or small flame' to came* a shattering explosion. Since It is difficult'to be certain that no spark or tablbhcd, using the four to one safety factor. After installation of thi^equipment, actual measurements are made jk> be certain that the design conditions Have been met. In general, the corrosive action of organic solvents b not very, great. However, this fac tor must be known sb that suitable piping and processing equipment can be provided. We can thus be assured that a corroded pipe or piece of equipment will not fail and pro duce hazardous conditions. 4 ...The Maximum Allowable Concentration and skin irritation properties of a solvent are part of the technical information which must be available if we are- to satbfactorily control exposures. We do not find . these properties listed in the handbooks the same as boiling point, vapor pressure, flash point, etc They' are just as important, however, and must be furnished as a part of the tech nical information which must -be in the hands of people who are developing, design ing and operating processing equipment or manufacturing, operations involving organic solvents. The Maximum Allowable Concen tration for different solvent vapors varies over a wide range--from a few partr. per million to thousands of parts per million. It is obvious that a piece of processing equip ment involving the use of a highly toxic solvent would, be designed quite differently than one using a solvent of low toxicity. The need for providing engineers and su pervisors with all. essential technical, infor mation-regarding solvents hak been 'empha sized. Perhapc it should be re-emphasized. All this information may be very helpful and useful if it is in .tbe- files of the safety en gineer-fir tbe industrial hygiene engineer. However, to be most useful; it must be in flame trill be present. It seems reasonable the hands of those persons who are actually that we should always operate this type of developing, designing or operating tbe proc equipment In such a way that the solvent esses which use these solvents. We have used vapors will always- be well bdow the lower several methods of supplying, suds informa explosive limit. Then we can be sure that if tion, which I will describe briefly. a spark, dr flame occun, there will be no pos All materials used in our plants are as sibility,of an explosion. We have fdt that it is desirable to maintain a four to one safety sctor?.oo, such exposures, and therefore we *hnlt;thc >apor conccntratkms In oven* or hdlar.;pieco>of-:procming equipment , to - *5;percent of the lower explosive limit. When newf ^equipment V is r being designed, v the amount of/solvent.' vjq>or to'. be released can usually;, bercalculated, and. from . this the anKJunt of 'exhaujt .rentilatioo can be es- signed a material number. For each'material a' 4 x 6 card U written by our Headquarters Engineering Department. On each card they lbt the following Information-- . Material Number Material Name . .. Caution. (A brief statement, of precautions to be observed In using this material) For Use By (Name: of. plant) r Furnished By (Name of. supplier) 20 35th National Safety Congress, 1947 Order From Supplier As (Supplier'* detignation or catalog number) Characteristics (A brief statement of the properties or engineering characteristics of the material). Application (A brief statement of where the material b used and its general applica tion). Specify As (How to spedfy the material on drawings or other written documents). You will note that the third item on thb material card b "caution." Before issuing any of these material earth, the Engineering Department .consults the Industrial Hygiene laboratory and they are furnished 'with a brief statement of the precautions that should be used for thb specific material. These sure brief statements such as "do not breathe va pors of thb material," or "avoid contact of thb material with the skin." Thb system has two advantages--first, it provides the Indus trial Hygiene Laboratory with Information about all new or changed materials that are used in the plants; second, a suitable warning limits, etc.' In each specification. More' re cently. wc are making reference in the speci fications to a Safe Practice Data Short. These Safe Practice Data. Sheets are provided'along, l with the process specifications to that-when a person has a process- specification be also has a safe practice data sheet. The Sate Prac tice Data Sheets list the following Informa tion about each, material that may involve any hazard-- Cootainexi and Storage Properties Fire Explosion Breathing Swallowing Skin Irritation Personal Protective Equipment Precautions ' First Aid We fed that thb provides fundamental tech nical information to all persons who are in volved in the design, development or opera tion of processing equipment. as to any hazards can be given. These ma terial cards are distributed to purchasing agents, materials and process engineers, de velopment laboratories, design and engineer ing departments and all other persons having a definite need for Information about mate rials. We have made a. number of references to the "engineering design" of equipment or processes involving the use of organic solv ents. With complete technical information available, the designer of the equipment b in a good position to take- advantage of any special characteristics which a material may Another method that b used for providing have. He can utilize equipment and methods good technical Information to the proper to suit the specific needs of the solvent in- persons in the organization b the data which ` .votved. If bc.b dealing with a solvent which are furnished with our Process Specifications. has a relatively low vapor pressure'and also Any process operation used at' any plant b a low order of toxidty, such'at kerosene, described on a.- process specification. Each there may-be no need for totally endoeed. process specification- b assigned a specific . equipment. If the solvent rhis at 'relatively number, and in general It can be said that Ugh vapor pramrt; and a .Ugh; order. of each of these process specifications describes toxidty, such as carbon disulfide, the design in detail any methods to bemused In prepar- er will recognize that totally enclosed cqtrip- ing a specific Item or producfc^Jfdr example, \ roent fa essential,, and In addition, local' ex one process specification may describe in de haust ventilation wQl be required wherever tail the method to be used for insulating vapors might escape. In the second case, a armature coils, and another may specify the ooosiderablc. expenditure of money 'will be details of the method of molding resins. necessary for thb type of eqtdjpment. Before Issuing or revising any of these process specifications, our Headquarters En gineering Department sends a copy to our Industrial Hygiene Laboratory for approval. It U checked to be certain that wherever hazardous materials are used, a suitable warn-* ing regarding the hazards has been Included. For a number of yean we Included certain technical information such a Maximum Al- . inwshlr Concentration, flash point, explosive It b surprising'the number of solvent ex posures that can be eliminated by proper design'of equipment 'dr shop ;layout.'.Of course, if ,we ,fnberj[t a piece of equipment, or uuurahcturing methods hate not ..been originally, set up to. eliminate ,the solvent ex posures, some means of protection against the exposures'must be devbcd.:3ddi methods' as - thejnstallation ^of; exhaust ventHating equipment, the use of^respirators, or theap- Automotive and Machine Shop Section 21 ^katiod of hand creams1 nuy- be indicated, mcdmes these methods -of protection may be satisfactory. In general, however, they require.an abnormal amount of supervision. "KJ be used as such. They may not be related in any way to any harmful effect' of the solvent. The second general method of determining . an exposure of an employee to a solvent va Wherever solvents arc used, it seems essen por is by a periodic physical examination. tialthat some quantitative measurements be This method depends upon making . some made to'establish-the extent of the exposure. specific determination which will give an in We may have good technical information and dication of early effects of the. solvent in the good engineering design, but we are never body. For example, blood counts, when certain-that vre have attained bur goal in properly performed, can be used to indicate controlling the solvent exposure unless the any early effects from exposure to a num actual exposure has been properly measured. ber of solvents, such as benzol. Other lab The fire hazard can usually be determined by oratory tests may be made, depending on the - irapcctioo.-If there p any possibility of an type of injury reaction that may occur in the explosion hazard, the measurement of vapor body from a specific solvent. If we depend concentration by use of ooe of the readily upon physical examinations to determine avaifat^ combustible gas indicators will de exposure to solvent vapors, they, obviously termine accurately whether satisfactory con must be 'done at rather frequent intervals, trol has been established. and the physical examination program must Unfortunately, it is a little more difficult continue indefinitely. to determine the exposure of a person. There I should like to emphasize the difference are two basic methods of determining the between these two general methods of con exposure of a person to a solvent. The first trol. By making measurements which indicate is by some measurement or inspection. Tor the exact extent of any individual person's. ample, we may determine by measurement- exposure, we are carrying out a procedure coe concentration of solvent vapor in the air which gives an indication rot over-exposure w__h_e_r_e__th_e__employ, ee works, or an insp4 ection before there is any-chance for a harmful rc- may reveal whether there is-any contact of action to occur in. tbchemployee. When we the solvent with the skin of the employee depend solely uponvp^ydcal examinations to Another method of determining the true ex determine these exposures, it b possible to posure of an employee b by some measure get an indication of over-exposure 6n!y alter ment which Indicates the amount of solvent some physiological change Iras takrarplaceJn vapor wh^dr has been breathed by the em the body. The desirability of the first proce ployee daring`his working period. Exposure dure b obvious.. to benzol, for example, may'be determined Even though we may not wish to utilize by a chemical , analysis of a urine specimen, the periodic physical examination as a means to determine the .ratio of organic sulfates to of controlling our solvent exposures, there b total sulfates In the urine. Some recent re- still a need for--proper prc-placemcni an^ search- week Jndkates that it .will be pos- periodic'physical examinations. The pre- tible to -determine, the- exposure of an cm- placement examination can indicate any ab- ployee to trichkrethytene vapors by a mess- normalities in an employee which later might urement qf the trichloracetic add in urine, be interpreted as the result of sock solvent A number of solvents increase the rate of exposure.. Likewise, certain physiological excretion of glucuronic add In the urine, \ahangcs may take place in an employee dur- There-- methods have not been extensively fmgfshb period of employment, even though used, but certainly will find wider applica- C there has been no harmful exposure. It- b tlori- In the. future. -We have found it very { desirable to detea there unrelated changes hdpful'ln controlling -benzol exposures to 'and make them known to the employee so determine the sulfate ratios In , the urine at that proper treatment can be Instituted and neriodk. intervals. .Whenever these determin- the employee will not have a ^fading that' tiqm indicate an excessive exposure, an In perhaps hb solvcpt exposure was a factor. vestigation!* immediately made to determine To summarize briefly, there are a wide whyT such . exposure' exists , and -. to instigate, variety of! organic solvents used In Industry corrective-measures. in relatively large quantities. From these sol v I ^should like'to "emphasize that these are vents a tremendous quantity of solvent yapors metlmds of determining exposure arid should sire liberated. To control exposures .io: these