Evanair-Conditioner
The 1938 Hupmobile Evanair-Conditioner, together with the concurrent Nash Weather Eye, were the automobile industry's first fresh-air hot water heating systems. Kelch fresh-air exhaust heaters had been available on Packard automobiles for several years prior to the introduction of these systems.
The Hupmobile system differed from the better-known Nash system by drawing up to 150 cubic feet (4.2 m3) of fresh outside air per minute through special hood louvers and thence through filters and heating coils into the passenger compartment. The Evanair-Conditioner, unlike the Weather Eye, was mounted entirely within the engine compartment, and the hot-water control switch was mounted on the dashboard. The very similar Weather Eye drew air in through a cowl ventilator, then filtered and heated the air in a unit mounted beneath or within the dashboard.
The then-revolutionary principles of both the Hupmobile Evanair-Conditioner and the Nash Weather Eye are still in use today in nearly every motor vehicle.