What is the definition of a volume damper? A volume damper is a device used in air conditioning and heating systems to control the flow of air in a ventilation duct. Generally, it is made up of a metal plate that is hinged in the middle, allowing it to open and close when needed. When the plate is open, it allows more air to flow through the duct, and when it is closed, it restricts the amount of air passing through the duct. Volume dampers can be manually or automatically operated, depending on the requirements of the system. They are typically used to regulate the amount of air in a single room, or to control the amount of air passing through an entire building. By controlling the air flow, the volume damper helps maintain an even temperature throughout the building, while also helping to reduce energy costs.