To cool hot materials, machinery or parts by moving cooler air across their surfaces. This is by far the most common use for air circulating fans. In the effective cooling of people, air movement utilizes favorable phenomena in human physiology.
Human bodies have a built-in temperature regulation system.
Their metabolism produces heat. In order to maintain thermal equilibrium, the body must lose heat exactly the same rate as its metabolism produces it. The body rejects excess heat by evaporation, convection, and radiation, all of which are affected by environment. A man working near a red ot furnace can better be protected by installation of a shiny aluminum shield between his position and the infra-red source. Fans will help the body lose heat by convection provided the temperature of the air is lower than the surface temperature of the skin.