air conditioning

System that controls the state of the air inside a building or vehicle. A complete air-conditioning unit controls the temperature and humidity of the air, removes dust and odours from it, and circulates it by means of a fan. US inventor Willis Haviland Carrier (1876–1950) developed the first effective air-conditioning unit in 1902 for a New York printing plant. The first fully air-conditioned high-rise building, the Milam office building in San Antonio, Texas, USA, was built in the 1920s.

The air in an air conditioner is cooled by a type of refrigeration unit comprising a compressor and a condenser. The air is cleaned by means of filters and activated charcoal. Moisture is extracted by condensation on cool metal plates. The air can also be heated by electrical wires or, in large systems, pipes carrying hot water or steam; and cool, dry air may be humidified by circulating it over pans of water or through a water spray.

The first air conditioners were used in 19th century textile mills, where a fine water spray was used to cool and humidify the atmosphere.

A specialized air-conditioning system is installed in spacecraft as part of the life-support system. This includes the provision of oxygen to breathe and the removal of exhaled carbon dioxide.

Outdoor spaces may also be cooled using overhead cool air jets.