What is a damper's primary function in an air duct system?

The primary function of a damper in an air duct system is to automatically close during smoke or fire conditions. Dampers are integral to smoke control systems within buildings, as they help contain smoke and fire, preventing it from spreading through the ventilation system. When smoke or a significant temperature rise is detected, the damper reacts by closing off the ductwork to compartmentalize the smoke and heat, enhancing safety for occupants and giving them more time to evacuate. This controlled movement is essential in maintaining effective fire resistance in a building’s design and mitigating potential fire hazards.

The other options do not accurately reflect the damper's primary function. While restricting cold air movement, filtering dust, or enhancing airflow may be functions of other components within an HVAC system, the essential role of the damper is its ability to act during emergency conditions by sealing off ductwork in response to smoke or fire detection.