Air-Conditioning The first air-conditioning system was installed in factories, but room air-conditioning began to appear in homes in the 1930s and spread rapidly in the 1950s. Fewer than one million homes had room air conditioners in 1950, but nearly eight million did in 1960, and more than half of all homes had some form of air-conditioning by 1975, as its status changed from a luxury to a necessity.

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