Document XzeZeyzyZ9q53DxXRvrE9a4VK

A KOWTXVr ' maoazixc ro* joro comACTOM conaxxm wtxh cosoceucuu, tfumnuu. ioro ncrnTunonw. Heating V ' . . JLKD entilating 1 i M-AINTIFFS f| < EXHIBIT IB coxamom*a. lumuocaATio*, rtrora, *r*n*o. mrnuiTio* PiLliiU^t THE INDUSTRIAL PRESS President ROBERT B. LUCHARS Vic-Prsident and Treasurer EDGAR A. 3ECKER Socretary ERIK OBERG Cditosial Editor CLIFFORD STROCK Associate Editor N. N. WOLPERT Bluklrvj Pfipyiftutiiofi HEATING AND VENTILATING is published mon`hly by The Industrial Press at 148 Lafayette Street. New York 13. N. Y. Yearly sub scription in the United States. Spain. South America. Mexico, and Canada. $2.00: in all other coun tries. $3.00. Single copies 30 cents. Entered os second doss motter. April 18. I92S. at tho Post Office. New York. N. Y.# under the oct of Mc-ch 3. 1879. A-lo&dUUtfy QcpieAessiaiiueS Eastern Representatives DWIGHT COOK HARRY J. TWINE M8 Lofoyette Street New York 13. N. Y. Western Representative GEORGE G. TURNER 228 North Lo So!le Street Chitoao I. III. CONTENTS FOR JUNE, 1944 VOLUME 41 N U MB E R 6 Oust Collecting System in Gunstock Plant ...................................................... <n)*min S. Utlin Grinding Wheel Quality Improved by Controlled Air............................... /. C. JStker 't-. *. 1* Dust as an Industrial Health Hazard ./......................................... f. It'. Ruickrntm ... Ventilation for Welding Booths ...A........... ?. r.t*l .1. sC-j/j...............* 51 55 57 *2 it. . Xmtfwist '` Vantllation for Radium Dial Storage .............................................. ................. ' 54 Cfl Again, On Again................................................... 1................................ J* 1. Wtttlcnitn ** Blueprint of Post-War Realities--Coal for Heating and Steam Generation .................................................................................................... Inrrn X. Soma Notes on Radiant Heating ......................................................................... r. W. Ktyntldt Weather Observers Have Difficulties ........................................................... 54 55 SI 81 Central Plant Heats <5 Buildings........................................................................... 82 F. n. Etllimirwtrlh Building Brazil ............................................................................................................ *. M Washington News ........................................................................................................... 86 Lt'ml F. Ovcrmrm News of the Month......................................................................................................... 88 Brief Reviews .............................................................................................. Newt of Equipment and Materials ....................................................................... $2 Degree-Days for April, 1M4 ..................................................................................... 100 With the Manufacturers ........................................................................................... to* Reference Data 271-272 ............................................................................................. 104 Personals and Personnel ............... }07 Getting Personal ............................................................................................................. 110 Army-Navy "E* Awards ............................................................................................. 110 New Catalogs ................................................................................................................... Ill Industrial Degree-Days for April, IMS ......... .*................................................ 113 Coming Events ................................................................ L-noynghf. 1944. by Tho Indutiriol Prett raecnXEC: MEMBER AgJit Surg of Ct/cuLl'on As Ppr NEXT MONTH'S ISSUE Process rU'tnt; is a subject that reac.hcs out into many Industries. Starting ''.Kit our July issue Hurry D. Unwin, of Albert Kahn anria'*-*l Architects t Fnclneers. Inc., xr 1I| present the first of go Dust as an Industrial Health Hazard F. W. HUTCHINSON A*Jrtnt Prof-*or Mechanical EngfnaarJng* Unlvaratty at California, fterltalay* Calif. . 1 I Xe rraee ch is nt of c. inne:rmoet to and The inuin essor. func- .isfied. r connc oq. .led in ` heal, main- ; 3 e i :cs the i heat ; corn- main* nes. andlcd opcral- ucd by ount of as the 'IF A ...........om LATINS THE health problem arising from dust in indus try is one of increasing seriousness. Socially, economically and legally it has become evident that immediate steps must be taken to combat the hazard itpresented by wholesale industrial exposure to the poeumoconiosis-produdng dusts. Pneumoconiosis, in many of its forms, is incurable. Thus consideration of the problem which it represents is based largely oo 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 point ofvicwthat most claims of silicosis arc unfair and in unscrupulous attempt to take advantage of them. The explanation behind an employer's unwillingness to acknowledge the hazard is not unreasonable. The dust diseases arc almost invariably of long duration and frequently arc not discovered until many years ifter exposure has ceased. Thus many employers ire 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 ycirs ago; at that time they were unaware of the hciith hazard associated with dusty atmospheres lnd consequently, though ihev might have had cscry desire to furnish their employees with full protection from occupational injury, they did not uke the "special care" which is now known to be necessary. Wilson states: "Most 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 `special care' will safeguard the 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 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, 25,000 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. The 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 present- day 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 it 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 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 "procressive" HriTu,,. 'Tti *Tiwr hint 1944 57 au m viewpoint it the one which has been most widely adopted but the possible future significance of the recent findings it promising. With reference- tjj: the "incurability" .'of 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 iu 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 tame 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 -*eferred 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 lunes of stone workers. In the 16th century Metallica" 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." fie exiled attention to the fact that the death rate among Carpathian miners was so great that a wife could often outlive six husbands. ' The passage of.time his 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 Barrc 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. Many estimates have been made of the number of persons exposed to hazardous concentrations of silica dust, but such estimates are 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 tilicotics 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. That silicosis is definitely related to a particular kind of occupational risk is demonstrated by the data from examinations (X-ray) of 2S00 workmen from all departments of a typical "heavy industry"; 5.8% had silicosis, but 90.0% of those affected were foundry workers. The gTcat 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 Hie silica group (above) showed only three causes ation of human values in the solution of engineering 0{ death (diabetes, appendicitis, digestive diseases) vfeich did not differ significantly from the general poup. The significance of these figures is at once problems. The above case is only one of a number of similar but less sensational cases which have shown tjiat ipparent when it is considered that an estimated there is a real possibility of contracting an acute 110,000 workers iri the United States have silicosis form of silicosis if work is in an atmosphere having in some degree. ^ Development of the Disease. The time required an extremely high concentration of siliceous dust. Experimentally the possibility of acute silicosis has for incapacitation due to silicosis has been the sub been demonstrated by laboratory tests on animals; ject of a great deal of attention, but as yet no gen for exposures of eight hours a day to concentrations erally accepted conclusions have been reached. Ap of 200 million particles per cubic foot or more it has parently the period of exposure preceding contrac been shown that the last stage of silicosis may be tion of the disease is a function of the dust concen expected in a relatively short time. tration, nature of the dust, nature of the work and Sire of Hazardous Dust. The importance of par individual physical idiosyncrasies. From a study of ticle size in determining the hazard associated with 9,800 stone-cutters in the Ruhr it is concluded that dusts has received a great deal of attention. Par 13 years exposure are required to show slight sili ticles 25 to 30 microns in size will usually settle out cosis and 20 years to cause incapacitation. This rapidly and are therefore not likely to be breathed same study reveals that 63 % of the deaths among in quantities sufficient to constitute a hazard. How silicotics occur from tuberculosis complications. In ever, particles of this magnitude (such as pollen of porcelain workers silicosis develops slowly but pro the Giant Ragweed or wood dust in carpenter shops) gressively;. the second stage is usually not reached may be responsible for hay fever or for various types until after 10 years. Among sandstone workers the of asthma. In general, particles greater than 10 mi minimal exposure has been found to be 11 years crons are caught in the trachea, large bronchi and while for iron miners an exposure of 4 to 5 years mucous membrane. Particles around 5 microns go miy be responsible for the appearance of lung to the respiratory tract, but few of them reach the changes 4 to 8 years after the exposure has ceased. alveoli where the 1 micron particles are most numer In contrast to the above relatively long incubation ous. Policard made a detailed examination of the periods are those found among workers engaged in lungs of two silicotic miners and found that 50% of sand-blasting and in the manufacture of abrasive the particles were less than .4 micron and 75% less soaps; in these occupations only 3 or 4 years may i precede the onset of the disease. Likewise, an exam ination of 175 men engaged in rock drilling showed 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 that 50% were affected in less than one year. tion of particle size in the inhaled dust--thus Poli- There is a good reason for believing that under card's findings may be applicable only for the con particularly heavy dust concentrations silicosis takes ditions under which the men whose lungs he an scute form and may appear after an exposure of examined had worked. The smaller particles arc only a few months. Not soon forgotten will be the obviously the most dangerous since, on a weight case of the Hawk's Nest Hydro Plant on the New basis, they offer a much larger surface than do the River. Some 4000 workers, mostly negroes, were larger ones. For this reason dust counts are of more employed for wages of $3.00 for a 13-hour day; in value in evaluating the hazard associated with a a relatively short time after completion of the tunnel dusty environment than arc gravimetric dust de work 475 of them were dead and an estimated 1500 terminations. others incurably ill. This case was investigated by The dust particles that are most effective in the a committee in the House of Representatives before causation of silicosis are of a magnitude so small whom witnesses testified that, "In the tunnel 10 that they arc not perceptible to the human eye. A drills were in operation at once and you could not micron is 1/1000 of a millimeter or about 1/25,000 (ce ten feet ahead of you even with the headlight of of an inch. As has been shown, the particles most ir the donkey engine". Workmen were so thoroughly important in silicosis arc in the neighborhood of .5 1C covered with a silica dust that "you could not tell a micron or 1/50,000 of an inch--this represents a di *n white man from a colored man, 15 feet away". It mension of the same order of magnitude as the wave i^ was this case that a senator from West Virginia dc- length of that form of radiant energy which wc i :c saribed as "the most horrible industrial disaster in recognize as light. If one cubic inch of quartz were :z the history of the world". It was of this case that broken into cubes .5 micron on a side enough par l- Representative Marcxntonio of New York charged ticles would be formed to create a silicosis hazard )Q tlat 169 workers had been buried unidentified be in a 250,000 cubic foot space. cause the undertaker had "lost" hit records. On the The determination of mean dust sizes was the basis of all evidence which has yet been brought for purpose of a scries of comprehensive studies con ward it would seem to the impartial investigator ducted by the U. S. Public Health Service: examina that the Hawk's Nest TunDcl should remain a tragic tion of 18,000 outdoor dust particles showed the icarioder to the engineer of the need for consider 0 ur.v I Mt' II I Kl V 1 04U median size to be .5 micron--nearly all were less 59 4- 4(1 :i r than 1.0 micron; in contrast, only 21% of 6,000 in- dmtriaj dust particles were leu than 1.0 micron, the majority being between 1 and 3 microns and the mean 1.5 microns. Hitch and Moke investigated foundry dusts and found that composition it a function of particle lize: the proportion of combustible matter and acid sol uble iron, carbonates, etc., increase with decreasing size; the proportion of day and other silicates varies without a definite trend with size; the quartz be comes less as the size decreases and for particles un der 2 microns (which comprises 90% of the total number) it is from 1/S to 1/2S of that found in the panicles greater than 10 microns. These findings emphasize the necessity of taking dust samples di rectly from the contaminated air and not utilizing "rafter" or any other kind of settlement sample which does not contain a representative size distri bution. Hazardous Concentration. Permissible concentra tions of dust vary with size, composition, and the dust retention characteristics of the individual. The latter factor is one which offers some hope from the standpoint of preventive medidne. Practically all that is known of the dust retaining characteristics of the human nose is attributable to the work of one man--G. Lehmann. This experimenter has shown that the dust fixation in the nose varies from 2% to 75% and is almost completely independent of such factors as the condition of the nasal secretion, the rate of air currents, the degree of concentration or chemical composition of the dust, the width or narrowness of the nasal passages; seemingly, fixa tion is a function of the vortex formation and re bound after passage through a restriction. A correlation between fixation and silicosis would seem to follow from the following tests: Of 46 stone cutters with fixations above 40% only two were found to have silicosis; of 31 stone cutters with fixa tions less than 29% only 2 were healthy. After ex amining the above data Lehmann concludes that, "applicants for work with poor dust fixation capacity should not be allowed to work where a menace of silicosis exists". As a result of 418 experiments with magnesium oxide and calcium carbonate, Carlton E. Brown gives the following relationships between dust re tention and other factors: Per Cent Retention is inversely proportional to 1. 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. This prob ably results from increase in respiration rate with minute-volume. Per Cent Retention is unaffected by 1. Volume per re.'piration. 2. Vita] capacity. 3. Relative humidity. The same investigator found that the percentage of magnesium oxide retained during normal bttathb while at rest varied little from about 60% lt i.ccc centrarion of 10 mg. Above 10 mg. the rttenbo changed but little, but as the concentration droppe below 10 mg. the retention rapidly approach* 100%. The relation between dust concentration and th incidence of silicoais has been studied by many in vestigators, but no general empirical relatiomhi has as yet been established. One commonly usa rule (proposed by Drinker) recommends the icrtp tancc of 5 million particles per cubic foot as th minimal permissible dust concentration for put silica and 50 million particles per cubic foot for dust that are very low in silica. Some evidence luggtsi that this rule is unduly conservative for dusts whic contain little silica and an alternative which is widel used is to limit the total dust count to a value sue that the product of the dust concentration by th percentage of silica be less than 5,000,000; this rol gives 100,000,000 particles per cubic foot as th minimal concentration for non-siliceous dusts. Physiological Effect. The lung condition know as silicosis results only from the inhalation of silica bearing dusts. Why silica possesses the ability t bring about this condition has been the subject c much investigation and theories of silicosis are i present responsible for considerable controversy Physiologically--excluding the effect of complies tions--silicosis affects the normal functioning of th body in the same way that the formation of seal affects the efficiency of a heat transfer device. 1 the heat exchanger the hot and cold fluids are sepa rated by an exchange surface and the deposit c scale on this surface reduces its effectiveness as a exchange medium. If the scale becomes sufficient! heavy it will be impossible to secure the transfer c enough heat to accomplish the purpose for which th exchanger was installed; similarly, the lune is a sui face through which oxygen is transferred from th air to the blood. The formation of scar tissue r< duces the effective transfer area and eventually th lung is unable to accomplish its purpose--death fror. suffocation is the result. `. Axbcstosis Asbestos dust is second only to free silica in thmagnitude of health hazard which it represents Asbestos is a fibrous material of varyine composi tion, but is usually made up of approximately 45 % magnesia, 40% silica and 14% water. Oxide of iror is frequently present and appears as dark particle: among the translucent fibers--the fibers are of such length and fineness that cloth weighing less than ox. per square yard has been made from them. The lung condition resulting from the inhahtior of this dust is known as asbestosis and resemble: silicosis in its main clinical aspects, but differ; dm to the enhanced rate of development. Under averagt industrial conditions the length of employment ir fatal cases is only about one-half that which i; usua /A far dliccxii. It is estimated that there are in the l^rtcd States approximately 10,000 men exposed to da hazard at a result of work in the insulating, j^ertos cloth, and similar industries. As is true of Jlicoiii exposure ciunmci, this figure does cot nle into account the number of persons exposed as i result of employment in the process industries 3n and tlx there asbestos finds use, under various trade names, 7 many Jj>_ is i filter aid. In one respect asbestosis it lest dead datioa(up ly than silicosis--that is, there is seemingly a lower aonly luserptibility to the supervention of pulmonary tu- die acctp. ktculotis. The danger of contracting the disease is oot at th< jpparently not influenced by either age or sex. Like for purt ^ silicosis, it is incurable and progressive; a case is re *t for dutu ported of a patient who was exposed to asbestos dust * *uggetu ^ jot one year and whose sputum showed the presence usts whici of isbestosis bodies fourteen years later. h is widely Very few data are available on the relation of dust value tudi concentration to the incidence of the disease. No on by tlx minima] safe concentrations have yet been set up this rule sod information is scant as to the conditions in those ot at the uses. phots where a hazard is known to exist. It has been determined, however, that the asbestos dust en on known countered in fabricating plants is free of silica when l of silica- air is floated at the breathing level and that the ability to dinger of the dust increases as the quality or length subject of of the fibers increases. sis are at ntroversy. complicar ' the Khcallarvaous Siliceous Dusts !' Many siliceous dusts other than quartz and asbes I -cale tos have been carefully investigated. Talc--a sili In cate containing 62% silica--has been shown to be arc sepa- responsible for a form of pneumoconiosis when in- leposit of jy bled in large quantities. One group of investigators ess as an B report that 50% of the talc workers whom they ex jfficicnily amined were affected and about 12% had tubercu ansfer of losis. The same report shows that talc containing **hich the 10% tremolite is much more dangerous than talc is a sur- containing 40% tremolite, but an explanation is from the lacking. .issue re- The action of cement on the lungs is not definitely ually the known. German investigators say that it produces ath from 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 a in the presents, omposily 43 % of iron panicles of such than 8 m. halation ' let JC . ..age ncm in is usual 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 and 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 m cotton spinning mills and report that the silicosis hazard is apparently negligible. Mincralogic analy sis of such dusts brought to light the interesting fset that thdr composition is similar to that of the soil In which the cotton was grown. Non-Siliceous Dusts Apparently there is a great difference of opinion as to whether or not non-siliceous dusts arc harmful either to normal or tubercular persons. The data arc so scant that a review of the literature mutt con sist essentially of a catalogue of the few and scat tered investigations that have been made of particu lar dusts. General conclusions 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 Urge American company which manufactures artificial abrasives led to the conclusion 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 I 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 claim 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 classifi 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, 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, precipitat ed calcium carbonate, gypsum and cement. A similar list of dusts has been prepared by Haynes who carried on a long scries 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 (in massive 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. ALPHABETICAL INDEX OF ADVERTISERS J A Acme Industries ........................ Air Conditioning Engineering Co. 116 Air-Mare Corporation ............. Airtemp Dir. Chrysler Corp. ____ 4 Airtberm Mfg. Co....................... ____103 :. Alco Valve Co............................... ____ 13 . American Air Filter Co., Inc. American Blower Corp............. 27 American District Steam Co. ------119 American-Marsh Pumps. Inc. . . * . American Rolling Mill Co. .. .... 14 V Armstrong Machine Works .. ------ 10 rr Automatic Products Co............. .. .. . B .; Badger Mfg. Sc Sales Co.......... .- Baldor Electric Co..................... i 1 Barber-Colman Co....................... \ ! Bell Sc Cossett Gp..................... " : Bethlehem Steel Co................. 1 Breldert. G. C.. Co................... 7 ! Brooks Equipment Co............. f | Bryant Heater Co..................... Buffalo Bolt, Co......................... c ` Buffalo Forge Co....................... Byers, A. M., Co......................... .- * G General Controls Co...................... Ceneral Electric Co....................... .' 107 * H* Hays Corp.......................................... . 117 Henry Valve Co.............................. Holcomb Sc Hoke Mfg. Co.......... .. 39 Howell Electric Motors Co.. Inside Back Cover I Ilg Electric Ventilating Co.......... Illinois Engineering Co.. Inc. .. Illinois Testing Laboratories, Inc. 114 Iron Fireman Mfg. Co................... .. 101 * Johnson Fan Sc Blower Corp. .. .. 36 Johnson Service Co..............Back Cover K Kewanee Boiler Corp.................... .. Korfund Co., Inc............................. 8 'L Ladish Drop Forge Co...................... 29 Penn Electric Switch Co.................. Porter. H. W., Sc Co.. Inc................... ug Powers Regulator Co........................... 117 Propellair, Inc...................................... R' _ Remor Manufacturing Co................ 1 Ric-wil Co.............................................. .1 s ; Sail Mountain Co............................. 1 * Sarco Company. Inc........................... , Sarcotherm Controls, Inc.............. li Smith. H. B.. Co.. Inc...................... Somers. H. J.. Inc............................. * Star Electric Motor Co..................... 21 Superior Sheet Steel Co................ T Taylor Forge Sc Pipe Works........ 21 Thrush, H. A^ Sc Co.......................... 22 Todd Shipyards Corp. (Combus tion Equipment Div.) ....'......... M Trane Co. . v............................. U Trerice. H. O.. Co............................... 1U. Tube-Turns, lnc.....................................-1 Tuttle Sc Bailey, Inc.......... .............. Carey, Philip. Mrg. Co....................... 31 Carrier Corporation............................ 33 3: Cash, A. W., Valve Mfg. Corp. ... 12 Chryiler Corporation ...................... < Classified Advertising.........................116 Continental Steel Corp...................... * Crane Co....................... ......................... 31 Crown Iron Works Co.......................... 115 i! Curti* Refrigerating Mch. Div. o Curtis Mfg. Co.................................. 18 Detroit Lubricator Co........................ 6 Detroit Stamping Co.............................119 Dravo Corporation ............................ . 91 Dunham, C. A.. Co.............................. 103 Economy Pumps. Idc............................. * Electric Auto-Lite Co......................... 112 Elgo Shutter Sc Manufacturing Co. * ::i<- Ellsworth Pipe Sc Supply Co.......... Emerson Electric Manufacturing 17 Co....................... '.............................. * Pr een&n Stnt-pr n; 111 i n ni ^ I rnn Leland Electric Co............................. 23 Link-Belt Co.........................L............. 16 ' U M. Marley Co., Inc.................................... Mario Coll Co.......................................... 11 Marsh. 3as. P,, Corp............................. 19 Mercoid Corp........................................ 37 McCord Radiator Sc Mfg.Co............... 117 McDonnell Sc Miller............................ 95 Minneapolis-Honeywell Regulator Co...........................Inside Front Cover Modine Manufacturing Co................ 12 Mueller Brass Co................................ 26 "' N Nash Engineering Co........................ SO Nelson, Herman. Corp..................... 18-19 U. S. Machine Corp........................... United States Air Conditioning Corp................................................. United StatesRadiator Corp........... * 5S W Wagner Electric Co............................. lKT?^ Want Advertisements ..................... Webster, Warren.. Sc Co....................... fw Weeks. B. H..'.................................... Westinghouse Electric Sc Manu facturing Co.......................... . White Rodgers Electric Co. Whitlock Manufacturing Co. Wing. L. J.. Mfg. Co...........................llHlvt Worthington Pump Sc Machinery Corp...................................................... Owens-Corning Fiberglas Corp. 99 Pacific Steel Boilers ____ Patterson-Keliey Co.. Inc. PnnFlnre Piirrm OlV Yamall-Warlng Co.................. 109-114-1111 York Heat Div., York-Shlpley. Lnc. Young Radiator Co.........................;. in' v -w-i