Document Gmko5bpVbO5vNjMdXj5nr557m

156 CHAPTER 8 1958:.Guide^K f_. 'real i"! pally from industrial plants, accumulating,during periods of exceptionally^?^ prolonged meteorological inversion and fog, contributed to the illness ofi ?; many persons, and- to the death of some who were especially susceptible: rrijr .- ' ir :y- Absorption of Solar Radiation ;J5r, Absorption of solar ultraviolet light by smoke and soot is recognized as a health problem in,many industrial cities. Measurements of solar, radia-.?; tion in Baltimore6 by actinic, methods demonstrated that ultraviolet light intensity in the country was 50 percent greater than in the city. In Newf York City7 a loss as great as 50.percent in visible light was found by photo-" electric; measurements. h;r: ODOR NUISANCE 2'.< i :.-J- A problem companionate with smoke abatement is the control of odor |Cl' nuisance in the neighborhood of industrial plants discharging noxious or ,r| offensive air contaminants. Community planning and zoning will avoid much of the difficulty in the future, but meanwhile many industrial cities;?? must resort to corrective measures by requiring installation of air cleaning^, devices, "alteration of "manufacturing processes, or'termination of the of-gr fensive operation in residential or commercial districts. ', Control of outdoor odor nuisance is especially troublesome because of'?? the extremely minute quantities of contaminant that are capable of offend;?;': ing through a wide area. New industrial chemicals with-strange or urP^ familiar odors tend to receive more attention from the neighborhood than|fJi the customary odors generated by well known processes and raw materials:?;; Methods of odor control currently in use include charcoal adsorption,?; j scrubbing towers and air washers, chlorination, condensation, masking,?; passage of the odorous air through combustion chambers, dispersion^; through a tall stack, and best of all, substitution of less offensive materials ?; whenever possible.8 9 10 11 ~ de control of air quality within buildings ventilated for human 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 position in the standards.of air quality for indoor comfort. How,;?; ever, the engineer will find, at times, that odors originating outside build?;:; ings in industrial or business districts may determine 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 controlig| 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 tp?? remote locations where it may cause property damage, nuisance, fire, ex?'., plosion, disease and even death. Jjd Tables 3, 4 and 5 give maximum allowable concentration; values forj| many industrial air contaminants. Some of these values have been prorji posed by ASA Sectional Committee Z37 on Allowable Concentrations ok| Toxic Dusts and Gases, and others by the Committee on Threshold Limits* of the American Conference of Governmental Industrial Hygienists. ThS Air Contaminants 157 values have been adopted by the American Conference of Governmental In dustrial Hygienists and by many of the official industrial hygiene agencies. It must be emphasized that these limits in the great majority of in stances are only suggested maximum working levels since they are estimates, based in many cases upon incomplete environmental and medical studies, where there is agreement between the ASA Standard Z37 and A.C.G.I.H. values, reliability of the ASA Standard is increased. The values are not fixed, but are subject to revision, upward or downward, with the develop ment 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 MA.C. is usually accepted as the average exposure value when the upper limits do not greatly exceed the M.A.C. 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 M.A.C. values may be quite different as to phys iological effects at other concentrations. In one instance the Selection of a limit may be predicated upon a discomfort factor, with a wide margin1 of safety before systemic effects would be encountered, while in another case the value represents an appreciable fraction of the concentration which may be associated with severe and irreversible injury. 5. These values are upper liinits; it is desirable to operate well below the levels ll the engineering and economic factors permit. The prudent engineer will incor porate a reasonable margin of safety in his estimates of ventilation capacity. J" o, v/oiumn 1 lists tne ASA Sectional Committee Z37 M.A.C. values; Column 2, those of the A.C.G.I.H. Committee on Threshold , *umn ^ gives the value in grams per cubic meter or ounces per 1000 cu ft for the corresponding A.C.G.I.H. limits. ., 'f' Columns 1 and 2 are respectively the M.A.C. values from the ASA and A.C.G.I.H. Committees. It will be rioted that Tables 3 and 4 have been extended greatly by the addition of threshold limit values adopted in April 1957 by the A.C.G.I.H. Tak|e 5, the M.A.C. values for industrial dusts as given were obtained m data of the A.C.G.I.H. Committee on Threshold Limits. C C.I.H limits for either gamma or Roentgen radiations are 0.3 roent gens per week. -P ProPerties and effects, with respect to health, of end of this chajA ^ contam'nants 7S available in publications listed at the of ^rp flammable gases and vapors ?en-t'*at*on's a primary requirement for minimizing the hazard tion k *Xpl0slon, ,ue to gases and vapors. The need for good ventila tion of knnrem->Ve<^- t^le 1186 other precautions, such as the elimina tion of cnfWK sources, segregation of hazardous operations, adop- Some safpf6 Du . nS eonstruction, and installation of automatic alarms, flammnbip eni=lneers regard over-ventilation of an operation employing Sv J1!? " a legitimate operating charge for the privilege or j using a dangerous process. However, it is not possible to