Computer fan

A computer fan is any fan inside, or attached to, a computer case used for active cooling. Fans are used to draw cooler air into the case from the outside, expel warm air from inside and move air across a heat sink to cool a particular component. Both axial and sometimes centrifugal (blower/squirrel-cage) fans are used in computers. Computer fans commonly come in standard sizes, such as 92mm, 120mm (most common), 140mm, and even 200–220mm. They are powered and controlled using 3-pin or 4-pin fan connectors.