Document R2ykRR5ERv41GjQR45mp0zgq7

522 . , Chapter 27 1945-Guide each rain-drop and the rain picks'up dust as it falls from the clouds to the' earth. However, it was found in recent studies5 that rain was not a good air cleaner-of the material below about 0.7 micron. DEFERENCES Bulletins, Industrial Hygiene Foundation, Inc., Pittsburgh, Pa. Determination and Control of Industrial Dust, by J. J. Bloomfield and J. M. Dalla Valle (U. S. Public Health Bulletin, No. 217, 1935). Journal of Industrial Hygiene and Toxicology, Harvard School of Public Health, Boston, Mass. . ... Reports of the National Silicosis Conference, Washington, D. C. {U. S. Division of Labor Standards, Bulletin No. SI). . , Symposiums on Silicosis, 1937 and 1939, Saranac Laboratories, Saranac Lake, N. Y. . Symposium on Tuberculosis, 1941, Saranac Laboratory, Saranac, N. Y. Industrial Dust, by Philip Drinker and Theodore Hatch (McGraw-TIill Co., N. Y.). Noxious Gases, by Y. Henderson and H. Haggard (Chemical Catalog Co., N Y.). Occupation and Health, International Labour Office. Preventive Medicine and Hygiene, by Milton J. Rosenau (D. Appleton-Century Co., N. Y.). Atmospheric Pollution of American Cities for the years -1931-1933, by J. E. Ives et al (U. S. PtfWt'c - Health Bulletin No. 224, March, 1936). CHAPTER 28 3,J&irCLeaning. 1et/iced Air Cleaners, Dust and Lint, Classification of Air Cleaning Media, Viscous Impingement Type Cleaners, Automatic Viscous Filters, Dry Air Filters, Electric Precipitators, Per formance. and Testing, Selection and Maintenance, Safety Requirements, Adsorption of Vapors Tj'OR the purposes of this discussion, an air cleaner is defined as a device jP' for capturing and removing solid matter from a stream of air. This solid matter includes fibrous material such as lint as well as particulate matter such as dust, fumes, smoke,, cinders, etc. Air cleaning is distinct . from air purification in that the latter deals with removal of harmful or unpleasant gases, vapors, or bacteria from an occupied space. Air pollution and purification are discussed in Chapters 2 and 27 and Air Sterilization in Chapter 36. In general, air cleaners are not installed in buildings for the specific ' purpose of improving the health of the occupants. However, in some cases air borne solid matter does affect health and the removal of such , matter from the air by means of cleaners is beneficial, such as pollen,-' house dust, and similar allergens which motivate attacks on persons having allergeric sensitivity1. The toxic elements in some war gases are in reality fine particles capable of air flotation. It is known by experience that air cleaners greatly reduce the rate of / dirt accumulation in buildings, but, in the present state of knowledge, an exact numerical expression for the cleaning effect of the filter cannot be given because of the many unknown or variable factors involved. For this reason air cleaners are usually selected on a basis of experience or judgment, guided by the results of various test procedures. AIR CLEANERS A typical air cleaner consists of a frame, which may be of metal, wood, ,, cardboard, etc., and a filtering medium. The frame is designed to support the medium in a duct or chamber forming part of the air conditioning or ventilating system, so that the air passes through the medium while en route to spaces to be ventilated. - Unit Air Cleaners or Filters , Many air cleaners are available in the form of units of convenient size for handling during installation, cleaning or replacement. Such units are usually designated as filters or unit filters. A typical unit filter may be 20 in. square and from one to several inches thick, depending on the manu facture and. proposed use. In large systems, a number of such units are installed adjacent to each other and collectively are called a bank of filters.. Ajr cleaners are commonly installed in the outdoor air intake ducts of buildings and, often, in the recirculating air ducts as well. Cleaners are logically placed ahead of heating or cooling coils and other air conditioning equipment in the system to protect them from dust. The character of the dust arrested by the filters in an air intake duct is likely to be mostly . ------rrV , . insoraers. oy a. a. Leopc American Medical Association, March 7, 1925. Vol. 84, p. 731-734).