Devi Enterprises Backward Curved Centrifugal Fan blades are the new standard in ventilation and air-conditioning. Backward Curved Centrifugal Fan features include both noise minimization and a further decrease in energy consumption. The low-noise centrifugal fans with forward-curved blades are also supplied with scroll housing. The centrifugal fans with backward-curved blades are designed as free-wheeling fans and do not require a scroll housing. For the centrifugal fans with external rotor motors, the motor is positioned in the impeller, resulting in optimum cooling of the motor as well as an especially compact design.