Back-Draft Damper Description Description It directs the air flow by opening and closing according to the air flow direction. Square and circular models are available Related products Air Handling UnitsElectrostatic Kitchen FilterUnit SeriesELECTROSTATIC KITCHEN FILTER Air Handling UnitsFAN SERIESEX-PROOF RADIAL SNAIL FAN Air Handling UnitsHeat Recovery Unit – Home TypeUnit SeriesHEAT RECOVERY UNIT (Domestic – Home Type)