The working principle of a centrifugal fan is basically the same as that of a turbo compressor, both because the gas flow rate is low, and the pressure changes little. Generally, there is no need to consider the change of gas specific volume, that is , the gas is treated as an incompressible fluid. Ventilation and induced air for boilers and industrial furnaces; cooling and ventilation in air conditioning equipment and household appliances; drying and selective delivery of grains, etc. Centrifugal fans can be made into two types, right -handed and left-handed. Viewed from the side of the motor: the impeller rotates clockwise, which is called a right rotating fan; the impeller rotates counterclockwise, which is called a left rotating fan.