Backward curved impeller fans with motors out of the airstream are suitable for a wide range of medium to high pressure ducted applications. Their impellers are capable of handling light dust in the airstream and have a high efficiency, non-overloading characteristic. This means that maximum power is drawn when operation is close to the middle of the fan pressure/volume flow characteristic. The motors are a standard industrial type, normally IP55 protection class, for three phase electrical supply.

Speed control is possible by variable frequency inverter drive, the size and cost of the inverter being minimised by this high efficiency, low power consumption fan.