Document MGJxaMYzGg1rVaY65Rpvw8OLj

FILE NAME: Philip Carey (PC) DATE: 1944 DOC#: PC003 DOCUMENT DESCRIPTION: Trade Publication Article - Heating and Ventilating , ~t* iy fiyt* 'i* : - i vV.* .le c tin io :> v m ix u itio i t f ' M ' Mi " , . 66 c I 1 i I '!li i S .i !i: *< y ) : ,.a b s o r b a ir - c o n d it io n in g n o is e s cv ctA vT.THE A LL A SB ES T O S U S T I C A L A ND I N S U L A T E D DUCT l.:M S w r r - * ^ 2m.v c K 5> ih w . <. OI mi -- Mfj C*, I. <*wa v ?! ;r 1 E?r I n radio stu d ios, K n p itiU . church. theaters. hotels, Wr;.-*. offices. hom e - w h m n f q u id w orking and living con i d itio n s nr req u ired --th is all asb esto s, prefabricated d u ct w ill lim inat n oil from tha air conveying system . to *a- I Carey duct is n devalaproent of tha Carry Research Labora 9 to ry an d acientificT U T d lestlrvg. I t is a n atu ral sou n d iff absorber a n on -con du ctor of sound, and non-resonating. It " quiets'* fan n oises and cu ts dow n speaking tube effects and elim in ates " cracking" due to changes in air pressure. By effectively absorbing noises, it perm its th e use of sm aller d u ct sizes w ith higher air velocities. T h is also solves d ifficu lt in stallation problem s where space is lim ited . B esides its absorption of noise. Carcyduct has m any oth er advantages over older and less efficien t m ethods. I t is fireproof; is quickly installed ; absence of noise in 51* e r e c tio n (u n a v o id a b le in h a n d lin g m e ta ls] p e r m its i n V sta lla tio n in occupied buildings such as hospitals.' stores, banks, etc.; conserves m etals; neat and com pact; can be painted to m atch w alls and ceilings; costs no m ore.'fre M quently less, than insulated m etal duct. - Tor tech nical details and further inform ation , sen d for s> " Carcyduct M anual." Address D ept. 19. r THE PHILIP CAREY MFG. COMPANY t-2 0e~VeW . 7reJ.cn ( m i 1173--l OCXIAND. CINCINNATI IS. OHIO A* < H# f U f C*T Cl' M"fs OS# r t i /<** t. Q. h At, it - > fmmk fesoAi SV, (l*"l^l,W. A A \. Ym V Ki I | ^ 4 H C<M'a * *<>< C.* ( ------ < V+C*aaJ U<(tlftal TfftMsk} i V; inclvdt It*t f( Cifff</*Kl in M lKir a mclfll vtfk. A! S. " T\ . : * v . * +- /V. . i u'* \ ; v v * .V l-' " L.-^ r y - X b ?V a /- f -- -'l - r-.i - :i t! t ; i kY " A .' A I ". ^ A ! r t --i--rr-v----- ..... _____ I. A KOXTX3.T k a q a z i x c rax tio tx tc x i JOtD C O X T K A C T O IU C O N U M U I WTTM ^Hea t in g AND V en tila tin g .. r C O F O C C X O A i. DTOST1UAL X O t w a i n U f l CtKAX. ATX C O H O IT IO ira iO . I G m O C U T l O H , W O W , K C A X LM a. T O r m - A T I O * 9*JdiiU c> l THE INOUSTRIAL PRESS President ROBERT B. LUCHARS Vico-President and Treasurer EDGAR A. BECKER Secretary CONTENTS FOR U1NE. 1944 VOLUME 41 NUMBER 6 Duct Collecting System in Gunatock Plant 51 JSenjtmin S. Sitiin Qrindlng Wheel Quality Improved by Controlled Air 55 /, C. *ker r ERIK OBERG Dust as an Industrial Health Hazard . ................ C dU aiiaL F. II'. HKidniiM i Ventilation for Waiding Sootha . . . . l .......... .'.i-.t4. Editor CFFORD STROCK A n o d a te Editor N. N. WOLPERT if . E. X n m u i ^ Ventilation for Radium Dial Storage . . . n............... Oft Again, On A g a in ......................... ............ Jkn /. Werl/enden Blueprint of Post-War Realities--Coal for Heating and . 6 Steam Generation .............................................................. . 65 Irwin X . Batmen HEATING AND VENTILATING U published mon*h!y by The Industrial Press a t 148 Loiayette Street. Now York 13. N. Y. Yearly sub scription in the United States. Spain. South America. Mexico, and Conoda. $2.00: in all other coun tries. $3.00. Single copies 30 cents. Entered os second doss matter, April 18. 1925. at the Post Office. New York, N. Y.. under the oct of Mc-ch 3. 1879. Some Notes on Radiant Heating ...................................... T. W. Reynold! Weather Observer* Have Difficulties Central Plant Heats 45 Buildings F. N. B tUiuftworth Building Brazil .............................. . Washington News ........................ . Latent F. Overman News of the M onth...................... Brief Reviews .............................. ............... News of Equipment and Materials . . . . . * S1 .. 81 .. 82 84 .. 86 .. 88 . . 90 . . 92 Degree-Days for April. 1 9 4 4 .................. . . . 100 A lo v U iiitu f (l& pA & i& niiiiiiei With the Manufacturers ........................ . . 104 Eastern Representatives DWIGHT COOK HARRY J . TWINE 148 Lafoyette Street Reference Oata 271-272 .......... , ............. Personals and Personnel ........................ Getting Personal ...................................... . Army-Navy "E" Awards ........................ - . 104 - . 107 . . 110 . . 110 New York 13. N. Y. New Catalogs ............................................. . . 111 Western Representative GEORGE G. TURNER Industrial Degree-Days for April, 1944 Coming Events .......... ............................... . . 113 . . 113 228 North Lo Salle Street Chicoao I. Ml. CcoyrigM. 19-44. by The Indusfriol Press c tn m t er~._L j-t._ n- >. l.- g n m r: MEMBER A tdil t u r t i u of CircuUMon l.ninatt PiOft NEXT MONTH' S ISSUE Process pliant; Is a subject th a t reaches out into many Industries. S lam ile v.lih our July issue H arry D. Unwin, of A lbert Kahn _______. 1 1 . . . . r r* s ... w - l ll - A -- --* c Dust as an Industrial Health Hazard F. W . HUTCHINSON A ssistan t Prof**or *f M *ck*nlc*l E ngineering, U n lv trtltT rf C allfem U . S erkaley, Calif. t Ve >ra ge ch is nt of i cione- :rmoet to ' and The : inuin essor. funcisfied, r conne on. .led in heat main- :es the i heac; commainncs. andlcd operaiited by ount of as the 'V x ....... om LATINO THE health problem arising from dust in indus try is one of increasing seriousness. Socially, tcooomically and legally it has become evident th at immediate steps must be taken to combat the hazard represented by wholesale industrial exposure to the pneumoconiosis-producing dusts. Pneumoconiosis, in many 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 recognition 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 of lung injury and equally difficult for the employer to defend himself against fraudulent claims; it has been said that silicosis claims constitute one of the most widespread of legal rackets. Workmen have bitterly opposed adoption of the exacting 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 print of viewthat most claims of silicosis are unfair and as unscrupulous attem pt to take advantage of them. The explanation behind an employer's unwillingness to acknowledge the hazard is not unreasonable. The dust diseases are almost invariably of long duration and frequently arc not discovered until many years after exposure has ceased. Thus many employers are now in the difficult and alarming position of fac ing claims for disease which is a result of exposure to conditions that existed in their plants 10 or 15 years ago; at that time they were unaware of the health hazard associated with dusty atmospheres and consequently, though they might have had every KE/tTING ANO VENTILA TIN G, JU N E , 1W4 desire to furnish their employees with full protection from occupational injury, they did not take the "pedal care" which is now known to be necessary. Wilson states: "M ost well-intentioned employers may be said 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 of '. . . available knowledge. . . only 'pedal care' will safeguard the interests of employer and workman alike." Recent interest in dust diseases has built up an eatensive literature; theories have been confirmed with experimental evidence and innumerable case histories of individuals and of entire 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 an 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 than the -cost of one damage suit. Jury awards in silicosis cases of $IC,000, $17,000, $22,500, $2S,000 and like sums are matters of record. In the St. Louis area alone there were, some time ago, over 2000 suits pending. A Missouri mining company, as another example, faced claims aggregating $5,000,000 and spent $500,000 in out-of-court settlements of a few of them. T he purpose of this article is to review the liter ature on the physiological effects of some of the haz ardous industrial dusts and to summarize presentday criteria acceptable as a basis for the design of dust control systems. Silicosis Silicosis is a 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 Progressive. The important facts about this disease are that, for practical purposes, it is progressive and incurable. The qualification " for practical p u rp o se s" 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 viewpoint is the one which has been most widely adopted but the possible future significance of the recent findings is promising. `I With reference-tjj: the "incurability" o f `silicosis, recent work has also indicated the possibility of a solution but it is as yet too soon to hold out hope for satisfactory medical treatment. One.promising method consists in the administration of thyroxene; the investigators 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 fibrosis 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 yet 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 medicine 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-- *the 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 mination occurs as a result of complications such as tuberculosis or heart disease; a definite correlation has been established between silicosis and tubercu losis, but an explanation is, as yet, lacking. With reference to tuberculosis a study of axe grinders and polishers showed a death rate of 1,900 per 100,000 from tuberculosis as contrasted with ISO per 100,000 for the general population of the same 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. Background 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 `eierred 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 his surgical knives were dulled by dust in the lungs of stone workers. In the 16th century Metallica" and, with reference to dust, warned his readers to beware because it "penetrates into the windpipe--eats 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 that a wife could often outlive six husbands. T he 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 that a threshold concentration of 5 million particles 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 of silica dust, but such estimates arc usually based only on industrial exposure. When account is taken of. the fact that 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 take account of the many workers exposed as a result of the industrial use of silica as a filtering agent. In one other respect the silicosis hazard has not yet been evaluated. As already mentioned there is a definite relationship between silicosis and tubercu losis. This fact leads to the probability that in any community in which there is a large number of silicotics there will be a decided familial tuberculosis hazard. Fortunately, however, this.danger is some 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 the 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 great importance of the silica hazard is clearly indicated from the following com parative mortality figures (from a 1933 publication of Hollis and Yule): 1000 for standard population (all causes for ages 20-65) 1984 for silica group The silica group (above) showed only three causes of death (diabetes, appendicitis, digestive diseases) srhich did not differ significantly from the general poup. The significance of these figures is at once apparent when it is considered that an estimated HO,000 workers in the United States have silicosis m some degree. Development of the Disease. The time required for incapacitation due to silicosis has been the sub ject of a great deal of attention, but as yet no gen erally accepted conclusions have been reached. Apparendy the period of exposure preceding contrac tion of the disease is a function of the dust concen tration, nature of the dust, nature of the work and individual physical idiosyncrasies. From a study of 9,800 stone-cutters in the Ruhr it is concluded that 13 years exposure are required to show slight sili cosis and 20 years to cause incapacitation. This me study reveals th at 63 % of the deaths among silicotlcs occur from tuberculosis complications. In porcelain workers silicosis develops slowly but pro gressively; the second stage is usually not reached nhtil after 10 years. Among sandstone workers the minimal exposure has been found to be 11 years while for iron miners an exposure of 4 to S years may be responsible for the appearance of lung changes 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 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 exam ination of 175 men engaged in rock drilling showed that 50% were affected in less than one year. There is a good reason for believing that under particularly heavy dust concentrations silicosis takes an acute 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 3.00 for a 13-hour day; in a relatively short time after completion of the tunnel work 475 of them were dead and an estimated 1500 others incurably ill. This case was investigated by a 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 see ten feet ahead of you even with the headlight of the donkey engine". Workmen were so thoroughly covered with a silica dust that "you could not tell a white man from a 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 at 169 workers had been buried unidentified be cause the undertaker had "lost" his records. On the basis of all evidence which has yet been brought for ward it would seem to the impartial investigator at the Hawk's Nest Tunnel should remain a tragic reminder to the engineer of the need for consider HFitiu ,- , " w tii A.TING. JU NE. 1944 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 t|iat 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 has 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 that 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 great 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, panicles 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 panicles 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 is very probable that the dust distribution in the lungs is a function of the distribu tion of panicle 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 arc obviously the most dangerous since, on a weight basis, they offer a much larger surface than do the larger ones. For this reason dust counts are of more value in evaluating the hazard associated with a dusty environment than are gravimetric dust de terminations. The dust panicles that are 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 imponant 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 wc recognize as light. If one cubic inch of quartz were broken into cubes .5 micron on a side enough par ticles w o u ld b e fo rm ed to c re a te 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 th in 1.0 micron; in contrast, only 21% oi 6,000 in magnesium oxide retained during normal breathio dustrial dust particle* were let* than 1.0 micron, the while at rest varied little from about 60% at a.ax c majority being between 1 and 3 micron* and the mean l.S micron*. Hatch and Moke investigated foundry dusts and found that composition it a function of particle size; centrarion of 10 mg. Above 10 mg. the rttrnoo changed but little, but as the concentration droppe below 10 mg. the retention rapidly approaches 100% . the proportion of combustible matter and arid sol T he relation between dust concentration and th uble iron, carbonates, etc., increase with decreasing incidence of silicosis has been studied by many in size; the proportion of clay and other silicates varies vestigators, but no general empirical rdatiooihi without a definite trend with size; the quartz be has as yet been established. One commonly use comes less as the size decreases and for particles un rule (proposed by Drinker) recommends the acctp der 2 microns (which comprises 90% of the total taace of 5 million particles per cubic foot as tb number) it is from 1/5 to 1/25 of that found in the minimal permissible dust concentration for put panicles greater than 10 microns. These findings silica and 50 million panicles per cubic foot for dusi emphasize the necessity of taking dust samples di th at are very low in silica. Some evidence suggest rectly from the contaminated air and not utilizing that this rule it unduly conservative for dusts whic " rafter" or any other kind of settlement sample " contain little silica and an alternative which tt wide! which docs not contain a representative size distri used is to limit the total dust count to a value sue bution. that the product of the dust concentration by tb Haiardovs Concentration. Permissible concentra percentage of silica be less than 5,000,000; this ml tions of dust vary with size, composition, and the gives 100,000,000 particles per cubic foot as th dust retention characteristics of the individual. The minimal concentration for uon-stliceous dusts. latter factor is one which offers some hope from the Physiological Effect. The lung condition know standpoint of preventive medicine. Practically all as silicosis results only from the inhalation of silica that is known of the dust retaining characteristics bearing dusts. W hy silica possesses the ability t of the human nose is attributable to the work of one bring about this condition has been the subject c man--G. Lehmann. This experimenter has shown much investigation and theories of silicosis are s that the dust fixation in the nose varies from 2% present responsible for considerable controversy to 75% and is almost completely independent of Physiologically--excluding the effect of complica such factors as the condition of the nasal secretion, tions--silicosis affects the normal functioning of th the rate of air currents, the degree of concentration body in the same way that the formation of seal or chemical composition of the dust, the width or affects the efficiency of a heat transfer device. I narrowness of the nasal passages; seemingly, fixa the heat exchanger the hot and cold fluids are sepa tion is a function of the vortex formation and re rated by an exchange surface and the deposit c bound after passage through a restriction. scale on this surface reduces its effectiveness as a A correlation between fixation and silicosis would exchange medium. If the scale becomes sufneienti seem to follow from the following tests: Of 46 stone heavy it will be impossible to secure the transfer c cutters with fixations above 40% only two were enough heat to accomplish the purpose for which th found to have silicosis; of 31 stone cutters with fixa exchanger was installed; similarly, the lone is a sui tions less than 29% only 2 were healthy. After ex face through which oxygen is transferred from th amining the above data Lehmann concludes that, air to the blood. The formation of scar tissue r< "applicants for work with poor dust fixation capacity duces the effective transfer area and eventually th should not be allowed to work where a menace of lung is unable to accomplish its purpose--death hot silicosis exists". suffocation is the result. As a result of 418 experiments with magnesium oxide and calcium carbonate, Carlton E. Brown Aabostosis gives the following relationships between dust re tention and other factors: Asbestos dust is second only to free silica n th magnitude of health hazard which it represents Per Cent Retention is inversely proportional to Asbestos is a fibrous material of varying composi 1. Respiration rate for rates below 20 per tion, but is usually made up of approximately 43 fc minute. An increase above 20 per minute magnesia, 40% silica and 14% water. Oxide of irot is apparently followed by no changes in is frequently present and appears as dark panicle: per cent retention. among the translucent fibers--the fibers arc of sue! 2. Minute-volume of air breathed. This prob length and fineness that cloth weighing less than f ably results from increase in respiration oz. per square yard has been made from them. rate with minute-volume. The lung condition resulting from the inhalatior Per Cent Retention is unaffected by of this dust is known as asbestosis and resemble: 1. Volume per respiration. * r 2. Vital capacity. silicosis in its main clinical aspects, but differs du< to the enhanced rate of development. Under averag 3. Relative humidity. industrial conditions the length of employment ir The same investigator found that the percentage of fatal cases is only about one-half that which is usua An | breathli^ t -t a ax-): C cntioo .oppaj lpprwchcd on and the f l / many b- -clauooihip oonly used f the acctp- pj oot a* t i e r for purt >t for duru :e suggests R usts which h is widely value such on by the ; this rule o t as the usts. .on known x of silica- ability to subject of sis are at ntroversy. complica- t the f .calc w.*c. In arc scpi- xposit of *ss as an jfficientlv ansfer of srhich the is a sur- from the -.issue re- ually the ath from a in the ^resents. :omposidy 43% : of iron particles of such than 8 m. halation les ic - -age nent ia >s usual bt silico*. I t is estimated that there are in the Uuted States approximately 10,000 men exposed to da hazard as a result of work in the insulating, ubestos doth, and similar industries. As is true of the silicosis exposure estimates, this figure does not tike into account the number of persons exposed as i resolt of employment in the process industries here asbestos finds use, under various trade names, isa filter aid. In one respect asbestos is less dead lythan silicosis--that u , there is seemingly a lower susceptibility to the supervention of pulmonary tu berculosis. The danger of contracting the disease is apparently not influenced by cither age or sex. lik e iXcosis. it is incurable and progressive; a case is re ported of a patient who was exposed to asbestos dust forone year and whose sputum showed the presence ofasbestos bodies fourteen years later. Very few data are available on the relation of dust concentration to the incidence of the disease. N o oioimal safe concentrations have yet been set up d information is scant as to the conditions in those phots where a hazard is known to exist. I t has been determined, however, that the asbestos dust cncoontcrcd in fabricating plants is free of silica when air is floated at the breathing level and th a t the danger of the dust increases as the quality or length ofthe fibers increases. Kkealfanaous Silieaous Dusts Many siliceous dusts other than quartz and asbes tos have been carefully investigated. Talc--a sili cate containing 62 % silica--has been shown to be responsible for a form of pneumoconiosis when in haled in large quantities. One group of investigators report that 50% of the talc workers whom they ex amined were affected and about 12% had tubercu losis. 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 particles per cubic foot produces a fibrosis ind pneumoconiosis, but few cases have been known to progress seriously. On the other hand, there is reason for believing that clay and slate dusts arc responsible for a high incidence of tuberculosis. Italian investigators have studied the dust hazard io cotton spinning mills and report that the silicosis hazard is apparently negligible. Mineralogic analy- of such dusts brought to light the interesting fact th at their composition is similar to that of the soil in which the cotton was grown. Non-Silicuous Dusts Apparently there is a great difference of opinion at to whether or not non-siliceous dusts are harmful either 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 th at have been made of particu lar dusts. General coodusions can not be drawn and an extension o f available data to dusts of even the tame mineral family is 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 inadence 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- cations: 1. Those causing an inert reaction, the amount of dust in the peritoneal cavity remaining approxi mately constant: soapstone, carborundum, jewel er's rouge, anthrarite 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, precipitat ed 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 toxidty as follows; precipitated silica, flint, sla te , h y d ro x id e, precipitated chalk, magnesium carbonate, carborun dum, calspar, emery, colloidal coal (in massive amounts). All of the respiratory disorders discussed above, together with many others which are caused by the inhalation of fibrosis-forming dusts, arc grouped un der the one broad term Pneumoconiosis. ir- -?r 1 At <r- T l-'fr- UT 'A-V hr dt 1 I..T%-' < f t !r-: fAcfe 14fl frisi MACHINE to heat-treat steel [ induction, lenite make better bomb cases t airplane propeller ends to r.Ein 115 seconds. Increase outjrcrill chucks 600 per cent. In ; to hundreds of manufne>faster production, lower Iimproved products, rinsides consist of expensive, t machinery. A motor-gener ator is its heart. To assure proper operating tem perature for the enclosed electri- 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 (see 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 by 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 but 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: Owens- Coming Fibcrglas Corporation, 1912 Nicholas Build ing, Toledo 1, Ohio; Fibcrglas Canada, td ., ^i Oshawa,Onlario. v h i f t h . R G L A S * |g ^ T " *T. M. JWg. u.s. r.<. Off. ND VENTILATING, JUNE, 1944 AIR FILTERS 99 1 ! T t i.H * J iii til ALPHABETICAL INDEX OF ADVERTISERS A A cm e I n d u s t r i e s ............................ 43 A ir C onditioning E ngineering Co.116 Air-Maze C orporation ...................... 40 A irtem p D ir. C hrysler Corp.......... 4 A lrth erm Mfg. Co............................105 A leo V alve Co................................. 11-24 A llen C o r p o r a tio n ......................... 13 A m erican A ir F ilte r Co.. In c. . . 27 A m erican B low er C orp..................... * A m erican D istric t S team Co.......... 119 American-M arsh Pumps. Inc. . . . . * A m erican R olling Mill C o . ........... 14 A rm stro n g M achine W o r k s ........... 10 A u to m atic P ro d u c ts Co....................... 10S B B a d g er M lg. Sc S ales Co. B a ld o r E le c tric Co............ .. 105 B arber-C olm an Co............................... 38 1 B ell Se. G o sse tt*Q > ............................. 35 B eth leh em S tee l C o . ........................ 97' B re id e rt. G. C., C o . ............................. * B rooks E qu ip m en t Co..........................114 B ry a n t H e a te r Co............................... 32 B llalo B o ltt Co.................................... 7 Buffalo F orge Co................................. 45 B yers, A. M.. Co...................................... * C : I C arey. P hilip . M lg. Co....................... 34 C a rrie r C o r p o r a tio n ............................ 33 C ash. A. W ., V alve Mlg. Corp. . . . 12 I C h ry sle r C orporation ...................... 4 C lassified A d v e r tis in g ......................116 C o n tin en tal S teel Corp..................... * C ran e Co....................... -...................... 31 C row n Iro n W o rk s Co......................... U S Curtis R efrigerating Mch. D ir. of C u rtis Mfg. Co.................................. 48 . X : d D e tro it L u b rica to r Co........................ 6 D etro it S tam p in g Co............................ 119 D ravo C orporation ............................ 93 D unham . C. A , Co. . . . . . . . . . . . . . 103 E E c o n o m y P u m p s . I n c ............................. * E le c tric A uto-Lite Co............................112 Elgo S h u tte r Sc M anufacturing Co. N E llsw orth P ipe & Supply Co.......... 17 El: E m erson E lectric M anufacturing Co................ ; Fre C l n b a e TV 1 1 1 n /> * ' Tr r t n G G eneral C ontrols Co.......................... 107 G eneral E lectric Co.......................... * H H ays Corp............................................. 117 H enry V alve Co................................. H olcom b H oke Mfg. Co............. 39 H ow ell E le c tric M otors Co.. Inside Back Cover I Ilg E lectric V entilating Co.............. * Illinois E ngineering Co.. Inc. . . . . Illinois T estin g L ab o rato ries. Inc. 114 Iron F irem an Mfg. Co. . J John so n F an Blow er Corp.......... 36 Johnson S ervice Co......... ...B a c k Cover K K ew anee Boiler Corp. .................... 8 K orfund Co., I n c . '.......... .................. 119 L L adisb D rop F orge Co. ................... 29 Leland E lectric Co. . . . ................... 23 L ink-Belt Co............ .. . A ............. 16 M M arley Co.. Inc.............. M ario Coll Co.................. ................... 41 M arsh. Ja s. P.. Corp. . . ................... 49 M ercoid Corp................... ................... 37 McCord R ad iato r Sc Mfg. Co............117 M cDonnell Sc M iller . . . ..................... 95 Minneapolis-Honeywell Regulator Co.......................... Inside F ro n t Cover Modlne M anufacturing Co.............. 42 M ueller B rass Co............................... 26 N N ash E n g in eerin g Co....................... 50 N elson, H erm an. Corp.....................18-19 O Owens-Corning F ib erg las C o r p ..; 99 P Pacific S teel B oilers ....................... 6 Patterson-K elley Co.. Inc. .-.......... t> A O* m n T v P en n E le ctric S w itch Co................. P o rte r, H. W .. Sc Co., I n c . ............ US P o w ers R egulator Co........................U7 P ro p e lla ir, Inc.....................................' R *2 R eznor M anufacturing Co.................. 1 Ric-wil Co............................................... .8. S S ail M ountain Co....................................* S arco Com pany, I n c . ....................... , S arco th e rm Controls, I n c . ............ JI S m ith, H . B.. Co., I n c . ................... Som ers, H . J.. I n c . ......................... S ta r E le ctric M otor C o . .................. 11 S u p erio r S h eet S teel Co................ T T ay lo r F orge P ipe W o rk s........ C T h ru sh . H . A - & Co............................ V Todd Shipyards Cotp. (Combus tio n E quipm ent Div.) . . . . " .......... M T ra n e Co. . , ................................... tf T rerice, H . O , Co................................ll*j ' T ube-T urns, I n c . ............................... * _ T u ttle & Bailey. I n c . ...................... U U. S. M achine Corp.......................... 'U nited S ta te s A ir Conditioning Corp. ........................................ .. U nited S tates R adiator Corp. . . . . S w W a g n er E lectric Co. ..................... l*j; W a n t A dvertisem ents ................ IH 3, W eb ster. W arren,. Co.......................XgS; W eeks, B. H. v W estinghouse E le ctric Sc Manu- factu rin g Co................................... W h ite R odgers E lectric Co.......... W hitlock M anufacturing Co. . . . W ing. L. J ,, Mfg. Co........................ H i 5 W orthington. Pump Si Machinery C o rp .................................................... m sz Y arnall-W aring Co..................109-11 Y ork H eat Div.. York-Shlpley. Inc. _ Young R adiator Co........................