Furnace filter, squirrel-cage fan wheel, and humidifier

Left, filter, centre, squirrel-cage fan wheel, and, right, an early humidifier

Left, filtering, to remove dust from the air was a new idea in the 1930s. Centre, the squirrel-cage fan wheel would produce sufficient air pressure to move large volumes of warm air through horizontal air ducts, making the winter air conditioner possible. Right, early humidifiers operated much the same as a pot of water boiling on the parlor stove. What was new here was a crude automatic water supply system.

Brochure, Howard Furnace and Foundries Ltd., T.H. Oliver Collection [detail]
G. Leslie Oliver, Ron Shuker, Nigel Heseltine
c. 1940
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