Document pBQVgDYBLm3Kgv59jL2Qky4oD

178 CHAPTER 9 1949 Guide see Air Conditioning of Farm Buildings, by F. L. Fairbanks (Agricultural Engineer, ing, November, 1937, p. 485). ' * Code of Minimum Requirements for Heating and Ventilating Garages (A.S.H.. V.E. Transactions, Vol. 41, 1935, p. 30). Airation Study of Garages by W. C. Randall and L. W. Leonhard (A.S.H.V.E. Transactions, Vol. 36, 1930, p. 233). A.S.H.V.E, Research Report No. 874--Carbon Monoxide Concentration in Garages, by A. S. Langsdorf and R. R. Tucker (A.S.H.V.E. Transactions, Vol. 36 1930, p. 511). A.S.H.V.E. Research Report No. 935--Carbon Monoxide Distribution in Rela tion to the Ventilation of an Underground Ramp Garage, by F. C. Houghten and Paul McDermott (A.S.H.V.E. Transactions, Vol. 38, 1932, p. 439). A.S.H.V.E. Research Report No. 934--Carbon Monoxide Distribution in Rela tion to the Ventilation of a One-Floor Garage, by F. C. Houghten and Paul McDer mott (A.S.H.V.E. Transactions, Vol. 38,1932, p. 424). A.S.H.V.E. Research Report No. 967--Carbon Monoxide Distribution in Rela tion to the Heating and Ventilation of a One-Floor Garage, by F. C. Houghten and Paul McDermott (A.S.H.V.E. Transactions, Vol. 39, 1933, p. 395). Carbon Monoxide Surveys of Two Garages, by A. H. Sluss, E. K. Campbell and Louis M. Farber (A.S.H.V:E. Transactions, Vol. 40,' 1934, p. 263). \ CHAPTER 10 AIR CONTAMINANTS Classification of Air Contaminants; Sizes of Airborne Particles; Air Pollution by Smoke, Ash and Cinders; Smoke Abatement; Odor Nuisance; Maximum Allowable Concentrations of Industrial Air Contaminants; Flammable Gases and Vapors; Combustible Dusts; Atmospheric Pollen; Air borne Bacteria THE normal constituents of the earth's atmosphere are oxygen, nitro gen, carbon dioxide, water vapor, argon, small or negligible amounts of other inert gases, hydrogen, variable traces of ozone, and small quanti ties of microscopic and submicroscopic solid matter, sometimes called permanent atmospheric impurities. From the viewpoint of the air condi tioning engineer, all other airborne substances may be termed contaminants. This term is applied preferably, however, to undesirable or chance im purities, since the occasion may arise for adding to the air controlled amounts of solid or gaseous diluents for the prevention of explosions; germicidal vapors or mists (aerosols) for bacteria control; masking sub stances'for odor control; or a substitute for one of the normal gases, as, for example, when helium is used to replace nitrogen in atmospheres for compressed air workers or divers. Control of the chemical quality of air is one of the functions of complete air conditioning, and some knowledge of the composition, concentration and properties of air contaminants under various circumstances is therefore essential. Air contaminants arise from the normal processes of wear, erosion> windstorm, sea-spray "evaporation, thermal disintegration, earthquake, volcanic eruption, combustion, manufacturing, transportation, agricul* ture, and the biochemical or biological processes of life. They are classr, fied at various times as organic and inorganic, visible or invisible, micro scopic or macroscopic, particulate or gaseous, toxic or harmless, beneficial. or destructive. The following classification is based chiefly upon the. origin or method of formation of air contaminants. CLASSIFICATION OF AIR CONTAMINANTS Dusts, Fumes, and Smokes are solid particulate air contaminants. Dusts are solid particles projected into the air by natural forces, such as wind., volcanic eruption or earthquake, and by mechanical processes, such as crushing, grinding, milling, drilling, demolition, shovelling, conveying, screening, bagging and sweeping. Some of these forces produce dust from larger masses, while others simply disperse materials that are already pulverized. Generally, particles are not called dust unless they are smaller than about 100 microns. Dusts may be of mineral type, such as rock, ore, metal, sand; vegetable, such as grain, flour, wood, cotton, pollen; or animal, such as wool, hair, silk, feathers, leather. Fumes are solid particles commonly formed by the condensation of vapors from normally solid materials such as molten metals. Metallic fumes generally occur as the oxides in air because of the highly reactive nature of finely divided matter. Fumes may also be formed by sublimation, distillation, calcination, or chemical reaction, whenever such processes create airborne particles predominately below the 1 micron size. Fumes permitted to age tend to flocculate into clumps or aggregates; of larger size, thereby facilitating removal from air. . .\ Smokes are the extremely small solid particles produced by incomplete combustion ` 179