Back Draught Damper 240mmThe non return damper flap on the pipe connector stops the intake of cold outside air as well as the return flow of exhaust air. The flaps automatically close as soon as the air flow ceases and open when the fan pushes exhaust air outside. The flaps need to be horizontally oriented in order to close effectively. In addition to being utilized for HVAC and Heat Recovery Systems, the professional metal connection with backdraft shutter can also be used