Document j0jJJb92N9m8gV2jOZjqBV2

152 CHAPTER 7 1950 Guide Growth and on Development, by K. D. Blackfan, C. P. Yaglou and K. McKenzie (American Journal Diseases of Children, 46:1175, 1933). Observations on the Control of Respiratory Contagion in the Cradle, by X. Rosenstern {Aerobiology, American Association for the Advancement of Science, Sym posium, 17:242, 1942). zt Physical Medicine, by F. H. Krusen (W. B. Saunders Co., Philadelphia and London, 1941). A.S.H.V.E. Research Report No. 1054--Fever Therapy Induced by Condi tioned Air, by F. C. Houghten, M. B. Ferderber, and Carl Gutberlet (A.S.H.V.E. Transactions, Vol. 43, 1937, p. 131). A.S.H.V.E. Research Report No. 1161Fever Therapy Locally Induced by Conditioned Air, by M. B. Ferderber, F. C. Houghten and Carl Gutberlet (A.S.H.V.E. Transactions,. Vol. 46, 1940. p. 307), ** Refrigeration for Anesthesia and Therapy, by L. W. Crossman and S. K. Safford {The Modem Hospital, 64:86, 1945). The Effect of Low Relative Humidity and Constant Temperature-on Pollen Asthma, by B. Z. Rappaport, T. Nelson, and W. H. Welker {Journal of Allergy, 6:111, 1935). * Hospital Air Conditioning, by C. P. Yaglou (The Environment and Its Effect Upon Man, Harvard School of Public Health, p. 244, 1939). *7 Principles and Practices of Inhalational Therapy, by A. L. Barach (J. B. Iippincott Co., Philadelphia, London, Montreal, 1944). m The Management of Pneumonia, by J. G. M. Bullowa {Oxford University Press, p. 260, 1937). ** What Are the Right Conditions for Comfort Cooling, by Cyril Tasker {Heat ing, Piping, and Air Conditioning, Aug., 1948, p. 84). 40 Odors Physiology and Control, by C. P. McCord and Wm. R. Witheridge (McGraw-Hill Book Co., New York, 1949). BIBLIOGRAPHY Studies in Air Hygiene, by R. B. Bourdillon, O. M. Lidwell and J. E. Lovelock with W. C. Cawston, L. Colebrook, F. P. Ellis, M. Variden Ende, R. E. Glover, A. M. Macfarlan, A. A. Miles, W. F. Raymond, E. Schuster and J. C. Thomas {Medical Research Council of Great Britain, 1948. Special Report Series No. 262). Ultraviolet Irradiation with Artificial Illumination, by Hans E. Ronge, Uppsala, Sweden, 1948, 191 pages. L'Hygiene du Batiment per L'Ultra-violet, by P. A. Burrucand, Centre Scientific et Technique du Batinent, Paris, 1949. Acceptance of Ultraviolet Lamps for Disinfecting Purposes, Council of Physical Therapy {Journal American Medical Association, 122:503-504, 1943). Evaluation of Methods to Control Airborne Infection, by J. E. Perkins {American Journal Public Health, 35:891-897,1945). The Present Status of the Control of Airborne Infections, by. Committee on Evaluation of Methods to Control Airborne Infections of the American Public Health Association {Journal American Public Health Association, 37:13-22, 1947). Progress in the Control of Airborne Infections, by Sub-Committee on Air Sanita tion of the American Public Health Association, read at Annual Meeting, 1949. To be published. CHAPTER 8 AIR CONTAMINANTS Classification of Air Contaminants; Sizes of Airborne Particles; Air Pollution by Smoke Ash and Cinders; Smoke Abatement and Air Pollution Control; Odor Nuisance; Maximum Allowable Concentrations of Industrial Air Contaminants; Flammable Gases and Vapors; Combustible Dusts; Atmospheric Pollen; Airborne 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 classi 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 prod-use 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 isa