A damper on ductwork is a device that is used to regulate the flow of air in a duct system. It is typically used to control the amount of air that is allowed to flow through the ducts, as well as to control the temperature and pressure of the air. Dampers can be manual or automatic, and they can be installed in a variety of locations, including the supply and return air ducts, as well as the main trunk line. The most common type of damper is the butterfly damper, which is a round disc that is connected to a shaft. The disc can be opened or closed by turning the shaft, which will then allow more or less air to flow through the ducts. Dampers are also used to control the amount of air that is allowed to escape from the ducts, which helps to reduce noise levels and energy costs. They are also used to prevent the buildup of condensation and to regulate the temperature of the air in the ducts.