Extractor fans with non-return valve

Non-return valve / shutters

— both the non-return damper and the automatic shutters perform the same function: they prevent air from flowing back into the room when the fan is not running. It prevents the penetration of unpleasant odours from other rooms through the ventilation. The difference between these options lies in the design: the valve is usually located behind the fan impeller and reacts to air movement, while auto shutters are most often installed on a decorative grille and open/close when the fan power is turned on/off.