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CHAPTER 7 1955 Guide 1IQ50V Fever Therapy Locally Induced by Conditioned Air, by M. B. Ferderber, F: C. Houghten and Carl Gutberlet (A.:S.H.V.E. Transactions, Voi. 46, 1940, p. 307). 44 Refrigeration for Anesthesia and Therapy, by L. W. Grossman and S. K. Safford {Th4e*TMhoedeEmffeHctosopfitLaol,w64R:8e6l,a1ti9v4e5)H. umidity and Constant Temperature on PolieL Asthma, by B. Z. Rappaport, T. Nelson, and Wl H. Welker (Journal of Allergy, 6:14141H,1o9s3p5i)t.al Air Conditioning, by C. P. Yaglou (The Environment and Its Effect Up4o7nPMrinacnip, HleasrvaanrddPSrcahcotoicleosf Pouf bInlihcaHlaetaioltnh,apl .T2h4e4r,a1p9y3,9)b. y A. L. Barach (J. B. Lippincott Co., Philadelphia, London, Montreal, 1944). 48 The Management of Pneumonia, by J. G. M. Bullowa (Oxford University Press, p. 4296W0, h1a9t3A7)r.e the Right Conditions for Comfort Cooling, by Cyril Tasker (Heal ingM, POidpoinrsg,PahnydsiAoloirgCy oanndditiConoinntgro, lA, buyg.C, 1. 9P48. ,Mpc. C84o)r.d and Wm. R. Witheridge (Me-' Graw-Hill Book Co., New York, 1949). il M . (`J .rr;. 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; Industrial Air Contaminants; Flammable Gases and Vapors; Combustible Dusts; Atmospheric Pollen; Airborne Bacteria; Radioactive Air Contaminants 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 quantities of microscopic and submicroscopic solid matter, sometimes called permanent atmospheric impurities. From the viewpoint of the air conditioning engi neer, all other airborne substances may be termed contaminants. This term is applied preferably, however, to undesirable or chance impurities, 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 substances 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, wind storm, sea-spray evaporation, thermal disintegration, earthquake, volcanic eruption, combusion, manufacturing, transportation, agriculture, and the biochemical or biological processes of life. They are classified at various times as organic and inorganic, visible or invisible, microscopic or macro scopic, 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 Dust, 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 msperse materials that are already pulverized. Generally, particles are not called unless they are smaller than about 100 microns. Dusts may be of mineral type, ucn as rock, ore, metal, sand; vegetable, such as grain, flour, wood, cotton, pollen; or ammat, such as wool, hair, silk, feathers, leather. fumes are solid particles commonly formed by the condensation of vapors from "finally solid materials such as molten metals. Metallic fumes generally occur as e oxides in air because of the highly reactive nature of finely divided matter, rerS may a*so frrae<f by sublimation, distillation, calcination, or chemical j "On, whenever such processes create airborne particles predominately below the micron size. Fumes permitted to age tend to flocculate into clumps or aggregates arKcr size, thereby facilitating removal from air. Smokes are the extremely small solid particles produced by incomplete combustion 151