Greenheck backdraft dampers are a type of mechanical device used to regulate airflow in a ventilation system. They are designed to prevent air from flowing in the wrong direction, which can be a major issue in ventilation systems. The damper is usually installed in the exhaust duct and is used to prevent air from entering the duct from outside. It is also used to control the amount of air that is allowed to enter the system. The damper is typically made of metal and has a flap or blade that can be opened or closed depending on the desired airflow. The blade is usually spring-loaded and is operated by a lever or knob. When the lever is in the open position, the blade opens and allows air to flow through the duct. When the lever is in the closed position, the blade closes and prevents air from entering the duct. Greenheck backdraft dampers are an important part of any ventilation system and can help to ensure that the air is flowing in the right direction and that the system is operating efficiently.