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146 CHAPTER 10 1965 Guide And Data Book . B. Z. Rappaport, T. Nelson, and W. H. Welker: The effect of iow relative namtdiiy auu'cuuawmt temperature Oil pollen asthma {Journal of Allergy 6: 111, 1933). Basic. Odor.-Research Correlations {Annals of the New York Academy ofScience 68:13, March 24,1954). L Rosenstem: Observations on the control of respiratory contagion in the cradle (American 'Association for the Advance ment of Science, Aerobiology 17:242, 1942). F. H. Kruaen: Physical Medicine (W. B. Saunders Co Philadelphia, 1941'. 1 L. W. Crossman and 8. K. Safford: Refrigeration for an esthesia and therapy {The Modem Hospital 64:86, 1945). A. L. Barach: Principles and Practices of Inhcdalionol Therapy (J. B. Iippincott Co., Philadelphia, 1944). - Cyril-Tasker: What are the right conditions for comfort cool ing? {Heating, Piping and Air Conditioning, August 1948, p. 84). CHAPTER 11 AIR CONTAMINANTS Classification of Air Confomxiwnfr; Sizes of Airborne Particles; Industrial Air Contaminants, Flammable Gases and Vapors; Combustible Dusts; Air Pollution; Radioactive Air Contaminants; Fallout; Atmospheric Pollen; Airborne Bacteria AIR is a m^hwniwd mixture of many ga^s.Normal air will . the air for purposes of disinfection, as well as materials added J\ consist of approximately 21 percent oxygen, 78 percent incidentally, through such' processes as combustion, manu nitrogen, 1 percent argon, and 0.03 percent carbon dioxide. In - facturing, transportation, and agriculture. addition, there axe trace amounts of other inert gases, includ ing hydnjgen, neon, krypton, helium, ozone,' and xenon, plus CLASSIFICATION OF AIR CONTAMINANTS varying amounts of water vapor and. small quantities of . microscopic and submicroscopic solid - matter, sometimes ' permanent atmospheric impurities.' - - Man is dependent upon air.to sustain life, but significant Air contaminants may be classified at various times as organic or inorganic, visible or invisible, submicroscopic, microscopic, or macroscopic,- particulate, or gaseous, toxic or hrtrmfaft A olftflnififtatinrihftflftd chiefly on the origin or method variations in the percentage composition of these normal con- ' stituetds may render the air unfit for his use. In addition, the presence of other foreign materials which may be classified-as contaminants may also render the. air unfit. The ventilating and air-conditioning engineer should recognize that air is sub-: of formation of the material consists of the following groups: (1) dusts, fumes, and smokes, which are solid particulate matter, (2) mists and fogs, which arvliquid particulate matter, >And (3) vapors and gases, which are nor^particulate. ject both to variation and contamination, since he is responsi Dusts, Fumes, and Smokes ble for both the quality and quantity of air provided. - Dusts are solid particles projected into the air by natural Variation in Air Composition forces such as wind, volcanic eruption, or earthquakes, or by meehsniftftl processes including crushing, grinding, demolition, The composition of air may be changed accidentally or de drilling, shoveling, screening, and sweeping. Some of these liberately. In locations-such-as sewers, sewage treatment forces produce dusts by the reduction of larger masses, while facilities, or utility tunnels, the oxygen content of the air may others simply disperse materials that are already pulverized. be reduced to such low levels that man cannot remain con- ' Generally, particles are not called dust .unless they are edous or survive. Man's normal respiratory functions also can / smaller than about 100 microns. Dustsmay-be mineral, such reduce the oxygen content in a rimilRr manner and cause a as rock, metal, or sand; vegetable such' as grain, flour, wood, buildup of carbon dioxide.' However, this is of most concern , cotton, or pollen; or animal including wool, hair, silk, feathers, in sealed atmosphere capsules. and leather. For the pilot of high altitude aircraft, air composition is - Fumes are solid particles commonly formed by the conden deliberately, changed by the'addition of Oxygen- When man is. sation of vapors from normally solid materials. Metallic fumes required to work at extreme depths. it is common to increase are generated from molten metals and usually occur as the the percentage of helium in his atmosphere and reduce the oxide because of the highly reactive nature of finely divided nitrogen concentration. matter. Fumes may also be formed by sublimation, distilla Air Contaminants tion, galvanization, or chemical reaction whenever `such processes create airborne particles. predominantly smaller Normal air contains varying amounts of foreign materials: than one micron. Fumes which are permitted to age tend to commonly referred to as permanent atmospheric impurities. flocculate into dusters of larger size. This phenomenon is used *niese materials can arise from such natural processes as ero often to facilitate the removal of fumes from air. ? sion, wind storm, sea spray evaporation, and volcanic enip-. Smokes are extremely small, solid particles, produced by in tion. The concentrations in the air will vary considerably, but, complete combustion of organic substances such as.tobacco, ysually will be far below the concentrations caused by man wood, ooaL oil, and other carbonaceous materials. The term made activity. ' . . . ' * smoke is commonly applied to the mixture of solid, liquid, Man-made contaminants are those materials, including - ' and gaseous-products, although distinction- is made! in the ozone and various chemical sanitizers, deliberately added to technical literature between such components as wot or g^^Tfai^cegeim! ruponnihitity (or tha chapter a wipwri to TC 4A laioatrial carbon particles, fly ash, cinders, tarry matter, imburned gases, and gaseous combustion .products. Smoke particles vary con* 147