Document GKGb4YV4nvXZg83rD9My3pBX4

American Society of Heating and Ventilating Engineers Guide, 1935 The A.S.H.V.E. Standard Code for Testing and Rating Air Cleaning Devices Used in General Ventilating Work1 explains how such devices are rated by (1) capacity in cubic feet of air handled per minute, (2) resistance par ticles SCALE. OF ATMOSPHERIC IMPURITIES F NUMBER SURFACE i OF FAR- AREA IN 1. TICLES (K SQUARE iwt can INCHES LAWS OF SETTLING IN RELATION TO 3 AIR CONTAINING .0006 GRAINS OF PARTICLE SIZE 1 IMPURITIES PER (limes of demarcation APPRO*.) . CU.FT(0NSITT-l) ................ Compiled by W. G; Frank and Copyrighted.Fig. 1. Sizes; and. Characteristics of Air-Borne. Solids in inches of water at rated capacity, (3) dust arrestance, the percentage relationship expressing dust removal efficiency at rated; capacity, (4) reconditioning power, the energy necessary, to operate the mechanism of Adopted 1934 by A.S.H.V.E. See Chapter 41. '272 Chapter 16--Air Cleaning Devices - v Utoihatic air cleaning device, and (5) dust holding capacity, the ^unt by weight of standard dust which a non-automatic air cleaning ferfee Will retain before reconditioning is necessary. O TYPES OF AIR CLEANERS According to the Code, the following four classifications are given the devices: rjass A. Automatic Type: In general all air cleaning devices which use power to utornatically recondition the filter medium and maintain a non-varying resistance to air flow. Class B. Low Resistance Non-Automatic Type: Air cleaning devices for warm air f maces unit ventilating machines and similar apparatus and installations in which a nJaaimum of not more than 0.18 in. water gage is available to move air through the air cleaning device. Class C. Medium Resistance Non-Automatic Type: Air cleaning devices for systems in which a maximum of not more than 0.5 in. water gage is available to move air through the air cleaning device. Class D. High Resistance' Non-Automatic Type: Air cleaning devices for the air intake, of compressors, internal combustion engines, and the like, where a pressure of 1 0 in. or more water gage is available to move air through the air cleaning device. Air cleaners may be also classified as follows: 1. According to principle of air cleaning. a. Air washers. b. Viscous air filters. (1) Unit type. (2) Automatic type: c. Dry air filters. 2. According to application. a. For central fan systems of ventilation and air conditioning. Filters of the automatic or semi-automatic type are usually recommended and are installed in a central plenum chamber. b. For unit ventilators. Filters of viscous unit or dry type, installed at inlet of individual units. c. For window installations. Self-contained units consisting of fan and filter, usually dry type, adapted to be placed in the ordinary window. d. For warm-air furnaces. Unit type viscous or dry filters placed in.small plenum chamber of warm-air house beating systems. e. For compressors and Diesel engines. Unit type viscous or dry filters, installed at air intake of compressors and Diesel engines. . f. For compressed air lines. Unit type viscous or dry filters. With the growing congestion of large cities and an industrial-growth throughout the entire country, the percentages of foreign material in the air, such as soot or carbon, which are unaffected by an air washer type of air cleaner, have increased. This has brought about the development of the viscous and dry type air filters which are part of many ventilating and air conditioning systems. AIR WASHERS AND SCRUBBERS Information on air washers will be found in Chapter 11. Scrubbers have not been used very extensively in the past for cleaning 273