Air-conditioning is an integrated, automated system for controlling the temperature, humidity, and cleanliness of air in a building. The concept arose from the known sensitivity of certain industrial processes to air temperature and humidity. In nineteenth-century textile mills, the use of water sprays to cool and humidify the air was a primitive attempt at air-conditioning. True air-conditioning was the invention of an American mechanical engineer,Willis Haviland Carrier. In 1902, only a year after graduating from Cornell University, Carrier installed a system for controlling air temperature and humidity in a printing plant in Brooklyn, NewYork. He patented his “apparatus for treating air” in 1906. Early customers for Carrier’s system included textile mills, where dry air could cause fibers to become unmanageable owing to the effects of static electricity. Interest was not restricted to cotton mills in the American South; the first foreign customer was a silk mill in Yokohama, Japan. In 1911, Carrier made public the formulae for his air-conditioning calculations, which still form the basis of air-conditioning technology today.

In order to capitalize on his invention, Carrier formed the Carrier Engineering Corporation with six partners in 1915 and began manufacturing air-conditioning units in 1922. By then, Carrier had invented a new machine—the centrifugal chiller. This refrigeration device provided the first practical solution to the problem of cooling very large spaces. As air-conditioning became well established in the industrial context, operators of other types of large buildings, such as theaters and hotels, became aware of the more general benefits of air-conditioning as a means of improving human comfort levels. The first public building to feature a Carrier centrifugal chiller was the J. L. Hudson Department Store in Detroit, Michigan, where three chillers were installed in 1924. Four years later, the Carrier company developed the “Weathermaker,” a small air-conditioning unit specifically designed for household use.