The CF Backdraft Damper attaches to inline ventilation systems to keep exhausted air out for good. When used in conjunction with a Can Fan and carbon Filter, the CF Backdraft Damper also helps control odors as it prevents any untreated air from escaping the enclosed area. The directional damper installs downstream from the fan: when the fan turns on, the airflow opens the damper, and when the airflow stops, the damper closes. This eight-inch CF Backdraft Damper fits any standard six-inch ventilation ducting.