Document 40JNyNyejbZMjpdVgXDMegnG

HEATING VENTILATING AIR CONDITIONING GUIDE 1944 occasionally the engineer is confronted with the problem of removing such material before the air in question is suitable for use in building venti lation. The physical properties of the particulate impurities of air are summar ized conveniently in the chart of Fig. 1. In the case of gases, the objectionable features are the injurious physiological effects and the danger from inflammability. (See Table 1.) Dust Concentrations It is customary to report dust concentrations as grains per 1000 cu ft or milligrams per cubic meter (except for dusts that may cause pneu moconiosis, which are reported as so many particles per cubic foot of air). Gas concentrations are commonly recorded as milligrams per cubic meter or as parts per million or as per cent by volume. Typical ranges in dust concentrations as now found in practical applications are given in Table 2. Table 2. Dust Concentration Ranges in Practical Applications3 Application Grains Per 1000 Cu Ft Mgs Per Cu M Industrial districts Dusty factories or mines____________________________ Explosive concentrations (as of flour or soft coal).. 0.2 to 0.4 0.4 to 0.8 0.8 to 1.5 4.0 to 80.0 4000 to 8000 0.4 to 0.8 0.9 to 1.8 1.8 to 3.5 10 to 200 10,000 to 20,000 1 grain per 1000 cu ft = 2.3 mgs per cubic meter; 1 oz per cubic foot *= 1 g per liter. The engineer frequently desires information regarding the effects of various concentrations of gases or dusts upon man, 'as the success of a particular installation may depend upon the maintenance of air which is adequately clean. At the present time there are several organi zations working on this problem all of them publishing literature of various kinds.1 References to books covering the hygienic_significance, determination and control of dust are listed at the end of this chapter. AIR POLLUTION AND HEALTH The prevention of various diseases which result from exposure to atmospheric impurities is an engineering problem. It is important for the engineer to insure, by proper ventilation, suitable environments for working or for general living. If the equipment used is to be successful, it must operate automatically a$ in the modern air conditioned theater or railroad train. In Table 3 are given data on permissible accepted standards for toxicity of gases and vapors which occur in industry. The prudent . engineer will design equipment using these bench marks as' the upper limits of pollution. In general it is good practice to avoid recirculation of air which originally contains toxic substances. Obviously there may be National Institute for Health. U.'S. Public Health Service; Division of Labor Standards. U. S. Depart ment of Labor: University of Toronto Medical School. Canada; Saranac-Laboratories. Saranac Lake. N. Y.; Industrial Hygiene Foundation, Inc.. Pittsburgh, Pa.; Harvard Schobl of Public Health. Boston. Mass.; Haskell Laboratory, Wilmington, Del.; and the Departments of Health and of Labor in the United States and in various provinces of Canada. 548 CHAPTER 28. AIR POLLUTION exceptions to this rule, but it is one which is generally being followed in cuArrfefenct tpiorancsticoef . the respiratory tract are associated with exposure to (hick dust, and may follow inhalation of practically any kind of insoluble and non-colloidal dust. Atmospheric dust in itself cannot be blamed for Table 3. Toxicity of Gases and Vapors3 Accepted Standards for Max. Allowable Average Concentration for Repeated Exposures Ammonia. Amyl acetate Aniline.-- Arsine...... Benzene.----------------- Butyl acetate. Carbon bisulfide.___ I Carbon dioxide..... Carbon monoxide. Carbon tetrachloride1 Chlorine------ -----------1 Dichlorbenzene........ Dichlorethyl ether... Ether...... ................... Ethylene dichloride Formaldehyde --I Gasoline....... .......... Hydrochloric acid.. Hydrogen cyanide__.| Hydrogen chloride... Hydrogen fluoride... Hydrogen sulfide Methanol............... Methyl bromide.. Methyl chloride___ | Nitrobenzene.'._____ Oxides of nitrogen.--] Phosgene_______ Phosphine_____ Sulfur dioxide__ Tetrachlorethane--..] Tetrachlorethylene. Toluene and xylene Trichlorethylene.... T{Muer^pcAhedanantpiicntaeeld.EfnrogmineeTrinhge, PVreovl.en57ti,onNoo.f O4,cAcupprailt,io1n9a3l 5D);isSeaasfeesC, obnyceRn.trRat.ioSnasyoerfsCaenrdtaJin. M--Co..mD.maollna Valle Toxic Substances used in Industry, by M. Bowditch, C. K. Drinker, P. Drinker, H. A. Haggard and H. Hamilton {Journal of Industrial Hygiene and Toxicology, Vol. 22. No. 6, June, 1940); and other authoritative sources. causing tuberculosis, but it may aggravate the disease once it has started.2 The sulphurous fumes and tarry matter in smoke are more dangerous than the carbon. Ift foggy weather the accumulation of these substances in the lower strata may be such as to cause irritation of the eyes, nose, and respiratory passages. The Meuse Valley fog disaster will probably become Peritoneal Tissue to Dusts Introduced as Foreign Bodies, by Miller 549