A back draft damper is a type of mechanical device used to regulate the flow of air in a ventilation system. It is typically installed in the ductwork of a home or commercial building, and its purpose is to prevent the backflow of air from outside the building into the ventilation system. The damper works by automatically closing when the pressure inside the ductwork is lower than the pressure outside, thus preventing the backflow of air. Back draft dampers are an important part of any ventilation system, as they help to ensure that the air inside the building is clean and free from pollutants. They also help to maintain a consistent temperature throughout the building, as the dampers help to prevent cold air from entering the building during the winter months. In addition, back draft dampers can help to reduce energy costs, as they help to reduce the amount of air that is lost through the ventilation system.