The WD-100 series backdraft dampers mount horizontally to allow vertical airflow up and prevent reverse airflow. Model WD-100 has no flange, model WD-110 has a flange on the discharge side, and model WD-120 has a flange on the intake side. These dampers open using air pressure differential (assisted by springs) and close using gravity. An optional motorpack converts the dampers to motorized operation.
