Document b52OkyZBBL8jBJE0NOX06Y5Jk

American Society of Heating and Ventilating Engineers Guide, 1937 The American Society of Heating and Ventilating Engineers has developed a code1 which explains how such devices are rated by (l) capacity in cubic feet of air handled per minute, (2) resistance in inches 1---------->----------------------------------------------------- Compiled by W. G. Frank and Copyrighted. ... Fig. 1. Sizes and Characteristics of Air-Borne Solids of water at rated capacity, (3) dust arrestance, the percentage relation ship expressing dust removal efficiency at rated capacity, (4) recon ditioning power, the energy necessary to operate the mechanism of "AS.H.V.E. Standard Code for Testing and Rating Air Cleaning Devices Used in General Ventilation Work (A.S.H.V.E. Transactions, Vol. 39, 1933). 308 Chapter 16--Air Cleaning Devices an automatic air cleaning device, and (5) dust holding capacity, the amount by weight of standard dust which a non-automatic air cleaning device will retain before reconditioning is necessary. CLASSIFICATION OF AIR CLEANERS According to the Code, the following four classifications are given the devices: Class A. Automatic Type: In general all air cleaning devices which use power to automatically 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 furnaces, unit ventilating machines and similar apparatus and installations in which a maximum 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 also be 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, as well as the non-automatic viscous unit or dry 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 or viscous 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 heating 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 ventilatingand air conditioning systems. AIR WASHERS AND SCRUBBERS Scrubbers have not been used very extensively in the past for cleaning air for ventilating purposes. However, new types have been developed '309