What device is used to control the volume of air in a duct system?

The damper is the device that is specifically designed to control the volume of air flowing through a duct system. Dampers can be adjusted to either restrict or allow airflow within the ducts to meet the specific heating or cooling needs of different areas within a building. They can be operated manually or automatically, often utilizing actuators, to ensure that proper airflow is maintained based on various conditions such as temperature, pressure, or occupancy.

In contrast, a filter is used to remove particulates from the air, helping to ensure that the air circulated within a space is clean. While it plays a crucial role in the efficiency of an HVAC system, it does not control or modulate airflow.

A blower is a fan used to move air through the ductwork but does not directly control the volume of air; instead, it generates airflow.

A valve is more commonly associated with fluid systems (like water) and does not typically play a role in the airflow regulation of duct systems. While it can control flow in piping systems, it does not apply to the control of air volume in ducts.

Thus, the damper stands out as the essential component for regulating air volume within duct systems.