For axial fans the concept of a propeller is applied. The flow through the impeller with the (propeller) blade is largely parallel to the rotor shaft, thus, the name axial fans. The rotating blade has a complex profile to achieve highest efficiency. Basically, the operating principle can be described like this: the air on the suction side flows constantly from all parts of the room to the inlet. Thus the inlet ring acts as a suction head. On the delivery side the air is ejected along the axis, effected by by the motion of the fan blades, pushing the air through the fan. Axial fans are mainly used for low pressure and larger air volumes. Ventilation, heating and cooling are thus the main application areas.