Document 91wRqvgZn74O6o6xRG8dZZZ35

FILE NAME: CERAMICS (CER) DATE: 1944 June DOC#: CER033 DOCUMENT DESCRIPTION: Journal Article - Dust as an Industrial Hazard l'e c lin o io * r > Heating and Steam Gene'J t.on w ith Coal n the subje-t ot t h i l m on th ' B l u e p r i n t nf P o t t - W a r R e a h t . e s . page 6b H t o t i i n ro * k o k t x it ..Heating V . . jLKD - entilating d rUAIMTlFF'S EXMIOIT cp JOTB COIOMCTOM c o w c r a o r m WITH f m o m i Q L pTDu 1MAi- AHO m i n i u n tom i. Jtt* coiuiiw *#. um ataA T io*. n r o r x y . jc c A lu ra . T ue ITU.TTO* P n ltlu IieA THE INDUSTRIAL PRESS President ROBERT B. LUCHARS Vice-President ond Treasurer EDGAR A. BECKER Secretory ERIK BERG C<LlL>aI s i &H Editor ' CLIFFORD STROCK Associate Editor N. N. WOLPERT ` c ALukim j. }h^ u m o* HEATING AND VENTILATING it published mon`hly by The Industrial Press ot KB Lofoyettc Street. New York 13. N. Y. Yeorly sub scription in the United Stotes. Spam. South Americo. Melico, ond C onoda. $2.00: in all other coun tries. $3.00. Single C O p io s 30 cent*. Entered os second doss motter, April 18. I92S. ot tho Post Office. New York. N. V., under the oct ot Mc-ch 3. 1879. A L ^eA U l^ Eastern Representatives DWIGHT COOK HARRY J. TWINE U8 Lafoystte Street New York 13. N. Y. Western Representative GEORGE G. TURNER 228 North Lo Solle Street Chicoao I. HI. CONTENTS F O R J U N E . 1 9 4 4 V O L U M E 41 . NU MB E R 6 Dust Collectin g S y r te m In Gunatock P lan t ....................................................... Srnf4min 5. H ilin Grinding W h e e l Q u i ll t y Im p r e v td by Controlled Air ................................ 55 /. C./tr Oust on Induttrlol H eolth H u r d . / . . . . . .............................. ' 87 F . II'. R m itin ttn . ^ V entilatio n for W oldlng Booth* . . . ............r . i L . . . . . . ............* *2 U. . ' Vontllotion for Radium Dial S to r a g e ..................................y ' 4 ........... Off Again. On A g a i n ..................................................... ........................ ; ...................... Blueprint of Poal-War Realltlta-- Coal for Heating and S te a m G eneration ....................................................................................................... i n rra X . R im tn . Som o Note* on R adia nt H aatln g ........................................................................... 81 T. It'. R tr*U i W eath e r Obaerver* H ave OlfBeultle* .................................................................. 81 Central P lant Heat <5 B u i l d i n g * ............................................................................ 82 F. H. EttU*tr*rlk M Building Braxll ................................................................................................................... W t i h i n g t o n N ew ............................................................................................................ ** L rrm t F. O+crmrm # N e w t of the Month ................................. *............................... ................... *...........** ^ Brief R eview* ........................................................................ .................................... 80 N e w t of E quipm ent and M aterial* ................................................ * .................... Degree-Day* for April, 1HA ....................................................................................... , 0 W ith the M anufacturer* .............................................................................................. 104 R e ference Data 271 272 ................................................................................................. 104 Personal* and P eraonnel .............................................................................................. 107 G ellin g P er son al ............................................................................................................... 110 Arm y-Navy - E " Award .............................................................................................. 110 N e w Catalog* ..................................................................................................................... 111 Inourtrlal Degree-Day* for April. 1 K 4 ......... .*.................................................. 113 Coming E_ vent.* .............................................................................................................................................. 113 C coyrigh t. I94 4 . by The Industrie! Press c .* m ! t/< T X M iso I '* * * ? MEMBER ............ 1 c;i*t''<>" lglir.lt P*p"` /RTk U \ i> NEXT MONTH'S ISSUE p r o c e i ' iMi-.nc Is a su b je c t t h a t renc.hcs out into n u n y Industrie. S iartn i" v. Itli our Ju ly issue H i r r y D. 'Unwlc. of A lb ert Kbn Aevo(io, , "> . ' r r h l l e c l s L E ng ineers. Inc., will presen i the first of \e irage ch is nt of cinne- :rmoet to and The inuin essor, func.isfied. r connc oo. .led in ' heal, main tes the i heat ; commainncs. andled opcrililed by ount o( as the ` IF ,T ......... om latino Dusi as an Industrial Health Hazard F. W . HUTCH IN SO N AMlrLant P rof.*or f M .ek an lc.1 I n o ln ^ fln Q . University rt Callfernl, Calif. THE heilth problem rising from dust in indus try is one of increasing seriousness. Socially, economically and legally * bccome evide"t jsmediate steps must be taken to combat tbe hazard Presented by wholesale industrial exposure to the pneumoconiosis-producing dusts. Pneumoconiosis, m Jeany of its forms, is incurable. Thus consideration of the problem which it represents is based largely on methods of dust reduction and removal and is therefore as much a responsibility of the engineer as h is of the physician. . . Fortunately, medical knowledge and engineering equipment have progressed to such a point that cognition of hazardous conditions and availability of methods for correcting them will now permit a complete, practical and economical solution of the problem. Unfortunately, prejudice and fear have surrounded the entire subject with such an aura of suspicion and distrust that neither workmen nor em ployers have until recently been willing to acknowl edge the hazard or recognize the need for preventive measures. In addition, the slow action of the disease coupled with failure on the part of many physicians to acquaint themselves with the proper diagnostic methods has made it difficult for the worker to es tablish his claim for compensation in the event ol lung injurv and equally difficult for the employer to defend himself against fraudulent claims; it has been said that silicosis claims constitute one ot the most widespread of legal rackets. . ., Workmen have bitterly opposed adoption of the ending employment qualifications and periodical physical examinations of those exposed to dust which are essential to medical control. Yet, it is essential that persons having a predisposition to tuberculosis or a low nasal filtering efficiency be excluded from the dusty trades. Similarly, protection of the worker demands that he be removed from exposure at the first indication of lung damage. Employers, on the other hand, have adopted the point of viewthat most claims of silicosis arc unfair and in unscrupulous attem pt to take advantage o t cm. The explanation behind an employer's unwillingness to acknowledge the hazard is not unreasonable. I he duu diseases arc almost invariably of long oration and frequently are not discovered until many years liter exposure has ceased. Thus many employers are now in the difficult and alarming position ot lac ing claims for disease which is a result of P $urf to conditions that existed in their plants or a years ago; at that time they were unaware ol the health hazard associated with dusty atmospheres >nd consequently, though they might have a every desire to furnish their employees with full protection from occupational injury, they did not u k e the "tpcdal care" which is now known to be necessary. Wilson states: "Most well-intentioned employers may be aid to have used `reasonable care' in past years and--considering their^lack of knowledge this is now their best defense in damage suits. How ever, from now on, with the spread o f . . . available k now ledge... only `.pedal care' will W thc interests of employer and workman alike. Recent interest in dust diseases has built up an extensive literature; theories have been confirmed with experimental evidence and innumerable case historic, of individuals and of enure groups are available. In contrast to the widespread ignorance of ten years ago, it would probably be difficult at the present time to find a worker in the dusty industries who has not at least heard of silicosis, or in employ er who is unaware of the crippling damage suits which will face him if his employees, through failure on his part to take the necessary preventive mea sures, contract the disease. The cost of dust control is often far less th in the cost of one damage suit. Jury awards in silicosis cases of SIC,000, *17,000, *22,500, *25,000 and like sums are matters of record. In the St. Lou** ar.ca alone there were, some time ago, over 2000 suits pending. A Missouri mining company, as another example, faced claims aggregating *5,000,000 and of them. . The purpose of this article is to review the luer- ature on the physiological effects of some oi the haz ardous industrial dusts and to summarize present- day criteria acceptable as a basis for the design of dust control systems. Silicosis Silicosis is * disease of the lungs caused by the inhalation of dust containing free silica. Some authorities believe, but this fact has not been estab lished, that the inhalation of silicates is also a caus ative factor. Incurable and Progresiive. The important facts about this disease arc that, for practical purposes, it is progressive and incurable. The qualification "for practical purposes" is necessary because recent in vestigations suggest that uncomplicated silicosis is not progressive; however, the continued existence of a case of silicosis without the onset of complications is so rare that, from the standpoint of social conse quences. the disease can in itself be regarded as pro gressive. In the medical literature the "progressive 57 *UT!N C AN 0 VEN T ILATI N G. JUNE. ' ............ viewpoint it the one -which has been most widely adopted but the possible future significance of the recent findings it promising. ``I . . . With reference tjj-.the "incurability" of tilicotit, recent work hat alto indicated the possibility of a solution but it is as yet too toon to hold out hope for satisfactory medical treatment. One.promiting method consists in the administration of thyroxene; the inveatigators report that: "Thyroid therapy may possibly not only prevent the development of silicosis, but may also arrest its further progress and possibly reduce to some extent the degree of fibrotit already existing." The above remarks on the "progressiveness and incurability" of silicosis have been included because they show how very far the medical profession has vet to go to achieve a solution of the silicosis prob lem. In terms of concrete present-day gain, the sum total of the best that medidne can now offer is not of much value. When dealing with contagious dis eases such as smallpox and Spanish influenza, it has been possible to achieve a satisfactory treatment as a first step toward the elimination of the disease itself; in the case of silicosis, a non-contagious dis ease, the only advance of real significance which is possible is an advance which must be brought about by the application of basic engineering principles-- 'th e reduction of dust concentrations at the breathing zone to a point such that a health hazard no longer exists; only in this way can silicosis be eradicated. If permitted to run its course without complica tion, silicosis will lead to death by suffocation--the lungs becoming incapable of maintaining a gas trans fer sufficient to sustain life. Usually, however, ter Mctallica" and,' with reference to dust, warned his readers to beware because it "penetrates into the windpipe-- cats away the lungs--implants consump tion in the body." He called attention to the fact that the death rate among Carpathian miners was so great th at a wife could often outlive six husbands. ' T h r passage of time has done little to alleviate the hazard. The development of pneumatic tools has led to a great increase in the dust concentrations at tending the grinding, polishing and cutting of stone. The death rate among Barre granite cutters, for ex ample, increased from 1.5 per 1,000 in the year 1890 to 19.6 per 1,000 in 1924, an increase attributable to the introduction of pneumatic equipment. When one realizes th at a threshold concentration of 5 million panicles per cubic foot is required to constitute a silicosis hazard (for dust made up of 100% free silica), it is then evident that there are many indus trial operations today which represent health haz ards that did not exist prior to the introduction of mechanical equipment. M any estimates have been made of the number of persons exposed to hazardous concentrations o( silica dust, but such estimates are usually based only on industrial exposure. When account is taken of. the fact th at 60% of the earth's crust consists of silica the likelihood seems great that such estimates are conservative. Lanza and Vane estimated that the number of industrial workers exposed to the silica dust hazard is in excess of half a million in those industries in which the processing or handling of siliceous material is of basic importance; this esti mate does not u k e account of the many workers exposed as a result of the industrial use of silica as mination occurs as a result of complications such as a filtering agent. tuberculosis or bean disease; a definite correlation In one other respect the silicosis hazard has not has been established between silicosis and tubercu yet been evaluated. As already mentioned there it losis, but an explanation is, as yet, lacking. a definite relationship between silicosis and tubercu With reference to tuberculosis a study of axe losis. This fact leads to the probability that in any grinders and polishers showed a death rate of 1,900 community in which there is a large number of tili- W, per 100,000 from tuberculosis as contrasted with 150 cotics there will be a derided familial tuberculosis per 100,000 for the general population of the same hazard. Fortunately, however, this.danger it some state. In this study the death rate of all workers in the dusty trades investigated was used. More strik ing figures and more significant ones were obtained from a Massachusetts investigation in which the tuberculosis death rate of 961 silicotic quarry work ers was compared with that for the general popula tion and found to be forty times as great. _ Baekgrcmnd and Extent. The name silicosis is of relatively recent origin, but the existence of the health hazard associated with dusty work has been recognized by medical men for many centuries. From the literature of the period we find that the Ptolemies knew of it. Pliny the Elder -cferred to the "stone cutters' disease" and devised a crude respirator for the protection of miners; Aristotle warned Greek workmen against the inhalation of dust. Hippocrates, three centuries before Christ, noticed that bis surgical knives were dulled by dust in the lunes of stone workers. In the 16th century . s~ ~' r.~ wre'e Dc Rc what lessened as a result of the long incubation period which is found with silicosis--by the time a workman's lungs have reached the stage at which tuberculosis is most likely to set in it is more than probable that his children will have grown past the age at which the danger of their contracting the dis ease is greatest. T hat silicosis is definitely related to a particular kind of occupational risk is demonstrated by tie data from examinations (X-ray) of 2500 workmen from all departments of a typical "heavy industry"; 5.8% had silicosis, but 90.0% of those affected were foundry workers. The gTeat importance of the silica hazard is dearly indicated from the following com parative mortality figures (from a 1933 p u b lic a tio n of Hollis and Yule): 1000 for standard population (all causes for ages 20-65) 19S4 (or silica group 967 for non-silica erouo / /. . / j b c rilica group (above) showed only three causes f Li/" 0( death (diabetes, appendicitis, digestive diseases) ytich did not differ significantly from the general poup The significance of these figures is at once apparent when it is considered that an estimated 110,000 workers in the United States have silicosis Jb aotne degree. . . . D evelopm ent of the Disease. The time required (or incapacitation due to silicosis has been the sub ject of a great deal of attention, but as yet no gentfilly accepted conclusions have been reached. Ap- psrtndy the period of exposure preceding contrac tion of the disease is a function of the dust concen- uadon, nature of the dust, nature of the work and dividual physical idiosyncrasies. From a study of 9,800 stone-cutters in the R uhr it is concluded that 13 years exposure are required to show slight sili cosis and 20 years to cause incapacitation. This wme study reveals th at 63 % of the deaths among tilicodcs occur from tuberculosis complications. In porcelain workers silicosis develops slowly but pro gressively; the second stage is usually not reached nnul after 10 years. Among sandstone workers the minimal exposure has been found to be II years bile for iron miners an exposure of 4 to S years miy be responsible for the appearance of lung dinge* 4 to 8 years after the exposure has ceased. In contrast to the above relatively long incubation periods are those found among workers engaged in c sand-blasting and in the manufacture of abrasive soaps; in these occupations only 3 or 4 years may precede the onset of the disease. Likewise, an examinadon of 17S men engaged in rock drilling showed that SOJo were affected in less than one year. There is a good reason for believing that under ptnJcularly heavy dust concentrations silicosis takes <c scute form and may appear after an exposure of only a few months. Not soon forgotten will be the case of the Hawk's Nest Hydro Plant on the New River. Some 4000 workers, mostly negroes, were employed for wages of J3.00 for a 13-hour day, in a relatively short time after completion of the tunnel work 47S of them were dead and an estimated 1500 others incurably ill. This case was investigated by i committee in the House of Representatives before whom witnesses testified that, In the tunnel 10 drills were in operation at once and you could not set ten feet ahead of you even with the headlight of the donkey engine". Workmen were so thoroughly If covered with a silica dust that you could not tell a 1C white man from * colored man, 15 feet away . It was this case that a senator from West Virginia de scribed as "the most horrible industrial disaster in the history of the world". I t was of this case that Representative Marcantonio of New York charged n that 169 workers had been buried unidentified be cause the undertaker had "lost his records. On the tans oi all evidence which has yet been brought for ward it would seem to the impartial investigator it the Hawk's Nest Tunnel should remain a tragic ttcundcr to the engineer of the need for consider- ,ij "ttiTl NG A.NO VENTILATING, JUNE. IWa ation of human values in the solution of engineering problems. The above case is only one of a number of similar but less sensational cases which have shown tjm there is a real possibility of contracting an acute form of silicosis if work is in an atmosphere having an extremely high concentration of siliceous dust. Experimentally the possibility of acute silicosis hss been demonstrated by laboratory tests on animals; for exposures of eight hours a day to concentrations of 200 million particles per cubic foot or more it has been shown th at the last stage of silicosis may be expected in a relatively short time. Size of Hazardous Dust. The importance of par ticle size in determining the hazard associated with dusts has received a gTeat deal of attention. Par ticles 25 to 30 microns in size will usually settle out rapidly and are therefore not likely to be breathed in quantities sufficient to constitute a hazard. How ever, particles of this magnitude (such as pollen of the Giant Ragweed or wood dust in carpenter shops) may be responsible for hay fever or for various types of asthma. In general, particles greater than 10 mi crons are caught in the trachea, large bronchi and mucous membrane. Particles around 5 microns go to the respiratory tract, but few of them reach the alveoli where the 1 micron particles are most numer ous. Policard made a detailed examination of the lungs of two silicotic miners and found that 50% of the particles were less than .4 micron and 75% less than 1 micron; his findings should be used with care, however, because it it very probable that the dust distribution in the lungs it a function of the distribu tion of particle size in the inhaled dust--thus Policard's findings may be applicable only for the con ditions under which the men whose lungs he examined had worked. The smaller particles are obviously the most dangerous since, on a weight basis, they offer a much larger surface than do the larger ones. F or this reason dust counts arc of more value in evaluating the hazard associated with a dusty environment than are gravimetric dust de terminations. The dust particles that arc most effective in the causation of silicosis are of a magnitude so small that they are not perceptible to the human eye. A micron is 1/1000 of a millimeter or about 1/25,000 of an inch. As has been shown, the particles most important in silicosis are in the neighborhood of .5 micron or 1/50,000 of an inch--this represents a di mension of the same order of magnitude as the wave length of that form of radiant energy which we recognize as light. If one cubic inch of quartz were broken into cubes .5 micron on a side enough par ticles would be formed to create a silicosis hazard in a 250,000 cubic foot space. The determination of mean dust sizes was the purpose of a scries of comprehensive studies con ducted by the U. S. Public Health Service: examina tion of 18,000 outdoor dust particles showed the median size to be .5 micron--nearly all were less 59 4H.. *. L,*J 1-i I'JJ i- ' i j M i . . H *ruaei were lesOsDt'hl a2n1 1f .n0 m* ic6r'0on00 tihne~ m ajority being between 1 i 7 ~c m en U m ieL T 3 m'CrOD` *nd , *nd Mok'. '`nvaugJted foundry dusts nd found that composition J, * function of panicle *ixe- c proportionof combu.dblc matter and add .olble iron, carbonate, etc., increa.e with dccrea.ing S h ' \ C P 'y TM 00 <>i day and other .ilicate. varied without a definite trend with .ire; the q u aru Z come, leu at the size decreases and for para'de. un numb T ^ ro-n`r (whlch 90% of the total number) it u from 1/5 to 1/25 of th ft found ,,The mnh! f ^ T CT 10 m!crons- Thee findings T it from ,eh CCe" ,ty- 0 i UkiDg d u ,t MraP,e` d l " S e r ^ S d `C con.tara,f ated *: -nd not utilizing whieh d o ! *ny 0 l h -r k b d f .ample _ Son DOt COnU,n * rePre.entative .ize distri- Conrenrrarion. Pcrmiuible coneentrat.on. of dust vary with .ize. composition, and the u.t retention charaaem tic. of the individual. The magne.ium oxide retained during ,, . while at rr.t varied little from about % b' U castration of 10 mg. Above 10 a r 11 ` ` changed but little, but a . the conre - rttrai below 10 mg. the m ention ra p id lT 0* df0?; 100%. p,dl> *pproicj The relation between dutt ______ inddencc of .Uicoai. ha. been stu d ie d ly tm tigators. but do genera! empirical r e l S bs s yet been established. One cornmn ? nilc (p ro v e d by Drinker) reTmmZ T ^ Uncc of 5 million particles per cubic foot ai , imnim*1 permissiWe dust concentration for ' a V7 !T,lJ,cl-501116TM`d'"ce.m silica and 50 million particles per cubic foot for du Sr " ** V1,` 1TM,e " " duly conservative for du.t. 5 conta,n little ..l.ea and an alternative which i. wid, used .. to limit the total dust count to a value i a t the product of the dus, concentradon fey percentage of silica be lei. than 5 000000- rk * *. 100,000,030 p, ra- d ,, 1 ' Id 't nC Wt,ch ffcrt hope from the standpoint of preventive medidne. Practically all fal Uk kn Wn f 1316 dun reta*n,ng characteristics of th eh u m in nose u attributable to the work of one . T a t ^ 'd t s f `S ' has .how,, ttoo 7/ 35%/0 aanndd is almost,DcothmepDle0tSeelyvianrdIee*pefnrodment2%nf ' 1, .nch ,iC,0; ` .** " o n of u i o > J S o ! 7 " ' , llr * ' d' i ' of concentration or chemical composition of the dust the -dd.k narrowness of the nasal passaged . L k 5 f T L MnCT r ? {or non-`:i`'ceous dusts. ..usdici os.s0rreifsu,lu onTly- rfrnomC thIueni*nh"aladriononofk,nLoCi brinvngk fUJU'k*W>y UllCa P" e" ability much *h m .Xh,t. condition has been the subjea , u ch investigation and theories of silicosis are EPhTysm5 lo,rI*ecSa^,,ynS,bleluido|-rDgcotnhscideerfafbeale ocfonctormove"rt ^cns-^ilicosis affects the normal funedoning of y, ,n kth e m Wly lhat formation of la. ffect* the efficiency of a heat transfer d e 4 t ] * " " *, f-- of the v o n c r ^ TM . " ^ / " : bound after passage through a restriction. A correlation between fiiation and silicosis would seem to follow from the following tests* Of cottett wj.h afc0V[ C o T o n i , . 1 7 c found to have silicosis; of 31 stone cutter, with fixa tions less than 29% only 2 were health " After aminmg the above data Lehmann concludes !hat applicant* for work w.th poor dust fixation capacity mratcedd Tbv) a,, e"xgcCkhranlhgCe hs0utrfaancde Ca0nldd ftlhueidjdeapreosiCt"P. scale on this surface reduces its effectiveneii .< 3 .`S ; " c w ' . ' ' lm 'ed ,0 w ort ' ' h " ' 1 >' A , a result of 418 experiments with magnesium : - ; d' and carbonate. Carlton E. Brown gises the following relationships between dust re tention and other factors: . f:z `c,::T ` Asbsfosis Per Cent Retention is inversely proportional to J. Respiration rate for rates below 20 per minute. An increase above 20 per minute is apparently followed by no changes in per cent retention. 2. Minute-volume of air breathed. Phis prob a ) results from increase in respiration rate with minute-volume. Per Cent Retention is unaffected by 1. Volume per respiration. 2. \ ital capacity. 3. Relative humidity. The same investigator found that the percentage of 60 magnitude of b e a ^ r M l r d ^ i c h ' i t St Caresn ^ Asbestos is a fibrous material of van-' eprcsent! tion. but is usually made Un f * * n? Cf mpW maznesia Tier y p ` aPProximatc!v 43 % Jmo,,s U, pr'`. rr/ zr yj,dh- ^ ofT s duf. rini ,0n r" Ull!np ir0m thc ;nhjl" i01 rilico is OWn JS ab ` snd resemble 0 the Ink US JT,lm d ,n i:jl " P" " ' du, inndduus, rrr)1, acnoCnCd ralC lfhdeeV]cen,gPth'conf* eLnl'npd|ocvrinacvneriagf,r 1 u l cases is only sbout one-half that which i; usua JU N T 1UI wr , - ______ _____ __ an ind i! ' many ta- 'clariooilup aonly tiled the acctp- ooc 11 tic for pure t for duiu * tuggeiu usti which ! 1 h ii widely value such on by the ; thii rule <x at the um. J on known l of tilica- ability to subject of sis arc It ntrovcriy. complica ' f the -cale -.e. In arc sepa- deposit of ess a; an jfficiemlv ansfer of vhich the is a sur- from the tissue re- ually the ath from a in the ; Dresents. ` tomposi- :!>% i : of iron . particles . of such : than 8 m. . halation les ie .aye n t m id - is usual - fcr silicoii. It it m ate d that there are in the liwied S utci approximately 10,000 men expoaed to a hazard at a result of work in the insulating, (thettos doth, m d similar industries. At ii true of x silicosis exposure estimates, this figure does not Dlc into account the number of persons exposed at i rcsolt of employment in the process industries rhcrc asbestos finds use, under various trade names, tss 6lrcr aid. In one respect asbestosis it less deadh thin silicosis--that is, there is seemingly a lower susceptibility to the supervention of pulmonary tu berculosis. The danger of contracting the disease it ipparcnily not influenced by cither age or sex. Like silicosis, it is incurable and progressive; a cate it re pined of a patient who was exposed to asbestos dust (orone year and whose sputum showed the pretence of asbestosis bodies fourteen years later. Very few data are available on the relation of dust moccntrarion to the incidence of the disease. No oisimal safe concentrations have yet been set up sod information it scant as to the conditions in those (bats where a hazard is known to exist. It has been deteunined, however, that the asbestos dust en countered in fabricating plants is free of islica when sir is floated at the breathing level and th at the dioger of the dust increases at the quality or length ofthe fibers increases. Khcalfanoous Siliceous Dusts ! ' Many siliceous dusts other than quartz and asbes tos have been carefully investigated. Talc--a fili ate containing 62% silica--has been shown to be responsible for a form of pneumoconiosis when in kaled in large quantities. One group of investigators ttport that 50% of the talc workers whom they ex amined were affected and about 12% had tubercu lous. The same report shows that talc containing 10^ tremolite is much more dangerous than talc containing 40% tremolite, but an explanation is lacking. The action of cement on the lungs is not definitely known. German investigators say that it produces only an inert deposit in the lungs, but American re ports show that the frequency of disability from respiratory diseases in cement plants is about double that found among employees in non-dusty manu facturing plants; absence from work was also twice as frequent. Yet animal experiments show that ce ment like limestone and gypsum produces an ad sorptive reaction; the dust disappears from the peritoneal cavity without the_ production of scar tissue. Slate (1/3% quartz) in concentrations of 700 million panicles per cubic foot produces a fibrosis sod pneumoconiosis, but few cases have been known to progress seriously. On the ether hand, there is reason for believing that clay and sla'c dusts arc 'sponsible for a high incidence of tuberculosis. Italian investigators have studied the dust hazard 'o cotton spinning mills and report that the silicosis hazard is apparently negligible. Mincralogic analy- * t i n r. KEATING AND VENTILATING. JUNE *is of such dusli brought to light the interesting fact that tha'r cotnposrrioa is similar to that of the soil in which the cotton was grown. Kioo-Silicvou* Dusts Apparently there is * great difference of opinion as to whether or not noo-tiliceous dusts arc harmful cither to normal or tubercular persons. The data arc so scant that a review of the literature must con sist essentially of a catalogue of the few and scat tered investigations that have been made of particu lar dusts. General coodusions can not be drawn and an extension of available data to dusts of even the same mineral family it hazardous. * German investigators have studied a number of different carbon dusts and rate them in the order of hazard which they represent: lignite, coal, graphite, charcoal, soot. A statistical study of the health hazard in a large American company which manufactures artificial abrasives led to the condusion that persons who have had pulmonary tuberculosis should not be al lowed to work where they will be exposed to dust from abrasives. The dust in this particular plant was aluminum oxide combined with silicon carbide and the incidence to tuberculosis was 1 1/2 times as great in the dusty departments as in the non-dusty. In this connection it is interesting to note that other investigators had previously reported aluminum ox ide as not being a factor in the production of silicosis -- thus a distinction must be drawn between the fibrosis-forming ability of a particular dust and its danger through increased susceptibility to pulmonary tuberculosis. This leads to the conclusion that the daim is unwarranted that a dust is not harmful merely because its reaction on lung tissue is inert. The U. S. Public Health Service has grouped dusts (siliceous as well as non-siliceous) in three dassifi- ca lio n s: 1. Those causing an inert reaction, the amount of dust in the peritoneal cavity remaining approxi mately constant: soapstone, carborundum, jewel er's rouge, anthracite coal, bituminous coal and precipitator ash. 2. Those causing a proliferative reaction, nod ules continuing to increase in size: quartz, chat and flint. 3. Those causing an absorptive reaction, dust disappears from the peritoneal cavity, but scar tissue is not formed: calcite limestone, prccipitated calcium carbonate, gypsum and cement. A similar list of dusts has been prepared by Haynes who carried on a long series of animal ex periments. He arranges them in order of toxicity as follows: precipitated silica, flint, slate, hydroxide, precipitated chalk, magnesium carbonate, carborun dum, calspar, emery, colloidal coal (n massi'c amounts). All of the respiratory disorders discussed above, together with many others which are caused by the inhalation of fibrosis-forming dusts, are grouped un der the one broad term Pneumoconiosis. c 1 SS JLMACHINEto heat-treat steel 1induction. ' v.auts make better bomb cases s^Bat airplane propeller ends to -Eia 115 seconds. Increase outriffl chucks 600 per cent. In ; to hundreds of manufocsfaster production, lower I improved products, insides consist of expensive, a* machinery. A motor-gener ator is its heart. To assure proper operating tem perature for the enclosed clcctri- >s 7 & ZV S ijitfe f & u c F * cal equipment, air is fan-circulated throughout the cabinet. This air must obviously be clean as a whistle. Dust-Stop* Air Filters inside the intake louvres (sec inset) make it that way. " Saves Possible Expense Dust-Stops arc one of the contributing factors to Tocco's remarkably low maintenance costs, made possible bv careful design and engineering of the complete unit. All users of machinery equipped with Dust-Stops have the advantages of a quick-change, standard size filler that can be easily removed when clogged with dirt accumulations and replaced with a new, clean Dust-Stop in a few minutes. ' Tocco is hut one interesting ex ample of how Dust-Stops can be designed and engineered into ma chines where dust must be control led. For further information on this type of application write: OwensCorning Fibcrglas Corporation, 1912 Nicholas Build ing, Toledo 1, Ohio; Fihr.rglns Canada, Ltd., Oshawa, Ontario/ ERG LA S * 0 T. m. m,. u. s. r.i. or. ANO V E N T I L A T I N G , J U N E , 1944 FA' A IR FILTERS 99 T>l*S\d AND V E N T I L A T I N G , J U N E 1944 380 FIGHTING AND CARGO SHIPS Theje shipt cq u v c ltn f in valu* to 1 0 0 0 liberty ships. ( A ) 3 Aircraft Carriers and 6 Cruisers 37 Destroyers 64 Destroyer Escorts 4 Cargo Ships 20 Tankers 54 Landing Ships 192 Liberty Ships Q,, / ALPHABETICAL INDEX OF ADVERTISERS V Mi I ? Co. 116 G General Controls Co. .. G eneral E lectric Co. . . . A irtem p Div. C hrysler Corp. . . . 4 H Penn E lectric Switch Co.............. 44' P orter, H. W,, & Co., Inc................. n s Pow ers R egulator Co......................... n ; Propellalr, Inc.......... A m erican D istrict Steam Co. Amerlcan-Marsh Pumps, Inc. . . . 27 . . . 119 . . . 14 B B adger Mfg. & Sales Co. H ays Corp........................ H enry Valve Co.......... Holcomb & Hoke Mfg. Co. .......... 39 Howell E lectric Motors Co., Inside Back Cover I Ilg E lectric V entilating Co .. Illinois E ngineering Co., Inc Illinois T esting L aboratories, Inc. 114 Iron Firem an Mfg. Co. . . . Barber-Colman Co. Bell & Gossett Ck>. B reldert. G. C.. Co. Byers. A. M., Co. .. 114 J Johnson Fan & Blower Corp. ---- 36 Johnson Service Co............. Back Cover K K ewanee Boiler Corp......... Korfund Co.. I n c . '........ ... 8 . 12 L Ladlsh Drop Forge Co............... . . . 29 Leland E lectric Co............... Link-Belt Co...................... R Reznor M anufacturing Co............. {, Ric-wil Co........................................... j'v . S Sail Mountain Co. . Sarco Company, Inc........................ Sarcotherm Controls, Inc................. IS Smith, H. B,, Co., Inc. Somers, H. J., Inc. . . . S tar E lectric Motor Co.................. u ) Superior Sheet Steel Co................... T Taylor Forge & Pipe W orks. Thrush, H. A., &. Co...................... y Todd Shipyards Corp. (Combus tion Equipm entDiv.) ................. y T rane Co. . t ..................................... y T rerice, H. 0.. Co.............................. u s Tube-Turns, Inc................................ j i T uttle & Bailey, Inc........................ U f Crane Co. . 116 . 115 f . 48 6 119 Dravo Corporation . 93 Dunham, C. A., Co. 103 Economy Pumps, Inc. 112 Elgo S hu tter & M anufacturing Co E llsw orth Pipe & Supply Co......... 17 Emerson Electric Manufacturing Co..................... .......... . Freem an Stoker Div. Illinois Iron 1. & Bolt Co......................................... m 12a M Marley Co., Inc...................... Mario Coil Co....................... Marsh, Jas. P.. Corp. . ........ Mercoid Corp...................... McCord R adiator & Mfg. Co. .. McDonnell & M ille r ................ Minneapolis-Honeywell Regulator Co......................... Inside F ro n t Cover Modine M anufacturing C o . __ . . 42 M ueller B rass Co.................... .. 26 ' N Nash E ngineering Co....................... 50 Nelson, H erm an, Corp.................. .18-19 0 Owens-Corning Fiberglas Corp. . . 99 P Pacific Steel Boilers ...................... 5 Patterson-K elley Co., Inc................ P eerless Pump Div., Food M achin ery Corp........................................... n o U. S. Machine Corp......................... United S tates Air Conditioning .* Corp.................................................. V United S tates R adiator Corp......... S' `v W ^ W agner E lectric Co...........................I6f ' W ant A dvertisem ents ....................u s W ebster, W arren, & Co.................\ i W eeks. B. H ...................................... W estinghouse E lectric & Manu facturing Co................................. 4HE W hite Rodgers E lectric Co........... W hitlock M anufacturing Co......... Wing, L. J,, Mfg. Co...................... u |. W orthington Pump & Machinery Corp.............................................. Y Yarnall-W aring Co................. 109-1I4-US York H eat Div., York-Shipley, Inc. _* Young R adiator Co........................ HJ Adcrtueaeot ippcgred la preceda* ^