What is a damper?

A damper is a valve or plate that stops or regulates the flow of air inside a duct, chimney, VAV box, air handler, or other air-handling equipment. A damper may be used to cut off the central air conditioning (heating or cooling) to an unused room or to regulate it for room-by-room temperature and climate control. Manually adjusted dampers have a simple knob or lever and are generally used for balancing airflow during commissioning and are not subsequently adjusted.

Motorised VCDs are normally part of an automatic control system to either modulate the airflow in a part of the system according to demand or to shut off a part of the system when not in use. VCDs can take the form of a simple flap on a single pivot, or multiple blades operated simultaneously via a gear or lever linkage system.