Document 7Obr34JM1r3XgZO3Qy18724aE

76 CHAPTER 7 1959 Guide neer, industrial executive, public health officer, city planning commission, and the community at large. Electrification of industry and railroads, increases in the use of domestic oil and gas furnaces, ami segregation of industrial districts arc gradually providing effective aid in the solution of this prob lem. In the large cities where nuisance from smoke, fly-ash, and cinders is more serious, limited areas obtain some relief by the use of district heating. (See Chapters 33, 34, and 35 for further discussion on fuel-burning technic.) Many present ordinances limit the Qumber of minutes in any one hour that smoke of a specified density (determined by comparison with a Ringelmann Chart which is described in Chapter 44) may be discharged. There is now considerable interest and activity in the con trol of air pollution factors in addition to smoke. Difficulty in the establishment of acceptable criteria for certain cor rosive and irritant gases, such as fluorides and the oxides of sulfur and nitrogen discharged with the gases of combustion, and the frequently complicated technical and economic prob lems encountered in control, have delayed the drafting and enforcement of legislative measures. Recent reports of an in creased incidence of diseases, such as pneumonia and lung cancer, in areas high in certain air contaminants, require further critical investigation before acceptance. The values finally adopted will undoubtedly be lower than the MAC (Maximum Allowable Concentration) limits for use in in dustry, because the exposure is continuous compared with the 8-hour day, 5- or 6-day week upon which MAC values are based, and because the exposed population contains individ uals with greater variation in age and health status. In foggy weather, or during an inversion of atmospheric conditions, accumulation of gaseous contaminants may.cause irritation of eyes, nose, and respiratory passages, and possi bly cause even.more serious physiological effects. The Meuse Valley fog disaster (Belgium 1930) and the Donors smog (Pennsylvania 1948) are classic examples in the history of gaseous air pollution. In both instances it is believed that irritant gases, principally from industrial plants, accumu lating during periods of exceptionally prolonged meteoro logical inversion and fog, contributed to the illness of many persons, and to the death of some who were especially sus ceptible. Absorption of Solar Radiation } Absorption of solar ultra-violet light by smoke and soot is recognized as a health problem in many industrial cities. Measurements of solar radiation in Baltimore* by actinic methods demonstrated that ultra-violet light intensity in the country was 50 percent greater than in the city. In New York City1 a loss as great as 50 percent in visible light was found by photoelectric measurements. ODOR NUISANCE. A problem companionate with smoke abatement is the control of odor nuisance in the neighborhood of industrial plants discharging noxious or offensive air contaminants. Community planning and zoning will avoid much of the diffi culty in the future, but meanwhile many industrial cities must resort to corrective measures by requiring installation of air clftaning devices, alteration of manufacturing processes, or termination of the offensive operation in residential or com mercial districts. Control of outdoor odor nuisance is especially troublesome because of the extremely minute quantities of contaminant that are capable of offending through a wide area. New indus trial chemicals with strange or unfamiliar odors tend to re ceive more attention from the neighborhood than the custom ary odors generated by well-known processes and. raw materials. Methods of odor control currently in use include charcoal adsorption, scrubbing towers and air washers, chlo rination, condensation, masking, passage of the odorous air through combustion chambers, dispersion through a tali stack, and best of all, substitution of less offensive materials whenever possible.*- * " u Control of air quality within buildings ventilated for hu man occupancy is discussed in Chapter 6. Tobacco smoke odors, cooking odors, and body odors are air contaminants of the nuisance type which now command a decisive posi tion in the standards of air quality for indoor comfort. How ever, the engineer will find, at times, that odors originating outside buildings in industrial or business districts may de termine the kind and capacity of equipment he must provide for a high quality air-supply installation. INDUSTRIAL AIR CONTAMINANTS Many industrial processes .are sources of contaminants. Their control is an important function of the ventilating or air-conditioning engineer, because the atmosphere within buildings is the medium whereby such finely divided matter is dispersed and transported from the source to remote loca tions where it may cause property damage, nuisance, fire, ex plosion, disease, and even death. Tables 3, 4, and 5 give maximum allowable concentration values for many industrial air contaminants. Some of these values have been proposed by ASA Sectional Committee Z37 on Allowable Concentrations of Toxic Dusts and Gases, and others by the Committee on Threshold Limits of the Ameri can Conference of Governmental Industrial Hygienists. The values have-been adopted by the American Conference of Governmental Industrial Hygienists and by many of the official industrial hygiene agencies. It must be emphasized -that these limits in the great ma jority of instances are only suggested maximum working levels since they are estimates, based in.many cases upon in complete environmental and medical studies. Where there is agreement between the ASA Standard Z37 and ACGIH values, reliability of the ASA Standard is increased. The val ues are not fixed, but are subject to revision; upward or downward, with the development of new information. There is by no means complete agreement regarding these values among responsible industrial hygienists. In applying these guide limits, the following factors must be . considered: 1. The duration of exposure is 8 hr a day for 5 or 6 days a week. 2. The measurements are indicative of the concentration in the breathing zone of the exposed person. 3. The MAC is usually accepted as the average exposure value when the upper limits do not greatly exceed the MAC value. For example, it cannot be' assumed that if 100 ppm is considered safe for 8-hour exposure, that 800 ppm for one hour will .be permissible. 4. Two substances with similar MAC values may be quite different as to physiological effects at other concentrations. In one instance the selection of a limit may be predicated upon a discomfort factor, with a wide margin of safety before systemic effects would be encountered, while in another case the value represents an appreciable fraction of the concentra- Air Contaminants 77 Substance Table 3----- Moximum Allowable Concentration of Gases and Vapors ASA Threshold limit Values ' ACGIH* 19S8 orris MAC b* ppo^ glot m or oz/IOOO OJ ft Threshold Unit Vatues ACGIH* IVS9 MAC ppm* by g/eu a or Oi/IOOO Ammnnin 200 10 1000 0.5 20 100 200 100 0.360 0.025 0.020 2.400 0.0012 0.012 0.015 0.012 0.070 1.050 0.360 100 25 Benzyl chloride...... ................ Butadiene (1,3-butadiene).... Butanone (methyl ethyl keButvl acetate (n-butyl ace- Butyl alcohol (n-butanol)... 1000 250 200 100 Butyl eellosolve (2-butoxy- Cellosolve (2-ethoxyethanol).. Cellosolve acetate (2-ethoxy- 50 5000 20 20 100 100 25 200 100 0 000? O'080 0.005 0.007 2.200 0.300 0.015 0.240 9.000 0.060 0.110 0.160 0.740 0.540 Chlorobcnzene (monochloroChlorofonn (trichlororaethane) 1-Chloro-l-nitronronaiM* Chloroprene (2-chlqro-l,3-bu- Diacetone alcohol (4-hydroxy4-methy!-2-pentanone)... Dichlorodifluoromet.hnna 1,2-Dichloroethaoe (ethylene dichloride^ * Dichloromonofluoromethane. . 1,1 -Dichloro-1 -nitroethanc.... 0.1 75 100 20 0.0004 0.350 0.490 0.100 25 400 100 100 400 400 0.05 0.090 0.022 0.410 0.400 1.350 0.690 0.0003 50 0.1 50 000 100 0.240 0.300 4.95 0.400 100 200 15 1 000 10 0.400 0.790 0.090 4.200 0.060 ACGIH -- American Conference of Governmental Industrial Hygienisto. Reprinted by pennbrioa from AHA Arcims / InduHrial ffatflk. f 857, VoL 18, pp. tti-S8S. b of rnpor or gae per million parts of nir by volume. Diehlorotetrafluoroethane___ * Diethylamine.............................. Difiuorodibromomethane . ... Diisobutyl ketone..................... Dimethylaniline (N-diraethyl- aniiine)..................................... Dimcthylsulfate......................... Dioxane (diethylene dioxide). Ethyl acetate........................ (x) Ethyl acrylate...................... Ethyl alcohol (ethanol)... Ethylamine............................ Ethyl benzene...................... Ethyl bromide.. Ethyl chloride!. Ethyl ether....... Ethyl formate.. Ethyl silicate.............................. Ethylene chlorhydrin.............. Ethylenediamine....................... Ethylenedibromide (1,2-di- bromoethane)......................... Ethylene imine.......................... Ethylene oxide.................. Fluorine................................ Fluorotrichloromethane. . Formaldehyde.................... (x) Furfural................................ Gasoline........................................ Heptane (n-heptane)............. Hexane (n-hexane)................... Hexanone (methyl butyl ke tone) .......................................... Hexone (methyl isobutyl ke tone).......................................... Hydrazine.................. Hydrogen bromide.. Hydrogen chloride.. Hydrogen cyanide. . Hydrogen Buoride.. Hydrogen peroxide. Hydrogen selenide.. Hydrogen sulfide.. . * Iodine.......................... Isophorone................. Isopropylamine___ * Mesityl oxide........ Methyl acetate... Methyl acetylene.. (x) Methyl acrylate... Methyl alcohol (methanol)... Methyl bromide........................ Methyl eellosolve (2-methoxy- ethanol).................................... Methyl eellosolve acetate (etnylene glycol monomethyl ether acetate)........... Methyl chloride........................... Methyial (dimethoxymethane) 1000 25 1 100 400 25 1000 25 200 200 1000 400 100 100 5 10 25 5 50 0.1 1000 5 5 500 500 500 7.00 0.075 0.860 0.290 0.025 0.005. 0.360 1.400 0.100 1.900 0.045 0.870 0.890 2.600 0.850 0.016 0.030 0.190 0.009 0.090 0.0002 5.600 0.006 0.020 2.000 2.000 1.80 CL4ip 5 5 10 3 1 0.05 20 0.1 25 5 25 200 1000 10 200 20 0.0013 0.017 0.007 0.011 0.002 0.0014 0.0002 0.030 0.001 0.140 0.012 0.100 0.610 1.650 0.035 100 1000 0.120 0.210 3.100 (z) These value* appeared in ACGIH tentative list for 19M * These items include chances made by ACGIH Cammitftm M Threshold Limits m 1858c