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1947-48 Theatre Catalog, 6th Edition, Page 418 (404)

1947-48 Theatre Catalog, 6th Edition
1947-48 Theatre Catalog
1947-48 Theatre Catalog, 6th Edition, Page 418
Page 418

1947-48 Theatre Catalog, 6th Edition, Page 418

Air Cleaning by High-Voltage Electricity

Dirt, Dust, and Smoke Removed from Air

In Ventilating, Air-Conditioning Systems

Electrical science has found a way to clean air of 85 to 90 percent of all dust and dirt, and deliver it economically and efficiently into theatres, ofiice buildings, factories, and homes.

The apparatus using the electrostatic precipitation principle is effective against particles as small as 1/250,000 inch, or even such finer materials as oil mist and tobacco smoke. Although the principle of electrostatic precipitation has been known since electrostatic fields were hrst discovered, the equipment was not available for utilization in the ventilation and air-conditioning field until about 1933 when the Westinghouse Electric Research Laboratories developed the equipment which made this principle suitable for those applications where air is to be

breathed by humans. In 1937 Westinghouse Precipitron units were installed for regular commercial installations in stores, office buildings, and so forth, and the use of this type of efficient air cleaning has grown by leaps and bounds. During the war time, the advantages of electrostatic precipitation were recognized for many war industries in order to get ideal manufacturing conditions. Since the war, the application of this type of equipment is well recognized and is being employed in pratically all types of industry, commercial and industrial businesses. The largest manufacturers of this type of equipment are the Westinghouse Electric Corporation, the American Air Filter Company, and the {aytheon Manufacturing Company.

DIRT IS BUILT UP on the ground rod and cell plates in the dirty-air side of the Westinghouse Precipitron. The parallel plates of the collector are alternately charged with 6,000 d.c. volts and spaced 5/16 inch apart. Since unlike charges attract, the positively charged dirt particles are attracted to the negative plate and grounded. Every! particle. regardless of size or makeup is here attracted.

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DIAGRAMATIC SKETCHES oi the electrostatic field in the air filter and of manner in which the dust and other particles polluting the air become charged and are subsequently precipitated.


Briefly, the electrostatic method of dust precipitation utilizes the electrical principle familiar to every high-school physics student: that objects with like electrical charges repel while objects with unlike charges attract each other.

Air to be cleaned is delivered into a dust charger section where electrostatic field is created by a row of grounded aluminum tubes and hair-thin tungsten wires (similar to that employed in incandescent lamps) carrying some 12,000 volts. The high voltage in the air gap between the tube and wire causes the air minutely close to the wire to become ionized, or broken down into positively and negatively charged particles.

The negative ions that are formed in the ionization chamber leap back to the positively charged wires, but the positive ions race in the opposite direction at a speed of 140 miles an hour toward the negative metal tubes.

In flight, these ions strike the particles of dust or other foreign matter in the coursing air and stick to them and ride along and imparting to the foreign matter itself a positive charge.

The air then enters a dust collecting section which consists of aluminum or steel plates alternately charged negative and positive and set edgewise to the air stream. One set of plates is grounded and the other set carries a voltage of some 6,000 volts. Since opposite charges attract, the positive particles are attracted to the negatively charged plates, where they cling until flushed down the drain. Dust particles are taken out of the air stream and the air leaving the unit is clean. The effectiveness of the cleaning of air is generally shown by the soiling ability of the air left in the air stream. With the advent of equipment using electrostatic precipitation, new and improved methods of efliciency test THEATRE CATALOG 1947-48
1947-48 Theatre Catalog, 6th Edition, Page 418