A fan blade will often rotate when exposed to an air fluid stream, and devices that take advantage of this, such as anemometers and wind turbines, often have designs similar to that of a fan. Fans produce air flows with high volume and low pressure (although higher than ambient pressure), as opposed to compressors which produce high pressures at a comparatively low volume.
Mechanically, a fan can be any revolving vane or vanes used for producing currents of air.
Most fans are powered by electric motors, but other sources of power may be used, including hydraulic motors, handcranks, internal combustion engines, and solar power. This may direct the airflow or increase safety by preventing objects from contacting the fan blades. Usually, it is contained within some form of housing or case. The rotating assembly of blades and hub is known as an impeller, a rotor, or a runner. A fan consists of a rotating arrangement of vanes or blades which act on the air. A mechanical fan is a powered machine used to create flow within a fluid, typically a gas such as air.
