Fanning air over blocks of ice to cool a room, a task performed by slaves for an 8th-century caliph (Khaleefah) of Baghdad, was one of the methods employed in the ancient world to subdue heat. The first true air conditioner, featuring humidity control, powered ventilation as well as mechanical refrigeration, was patented in 1902 by the American inventor Willis Carrier. The addition of a dust filter in 1906 to improve the air in textile mills led to the term 'air conditioning'.
Air conditioning was initially invented by Willis Carrier to help a Brooklyn, New York, printer to get decent colour during hot, humid weather. Air conditioning wasn't used for cooling people until 1924 when it made its debut at the J L Hudson Department Store in Detroit, Michigan.