Manual volume dampers are set once by a balancer; motorized control dampers modulate for zoning, economizers and VAV; backdraft dampers allow flow one way only. Fire dampers close on a fusible link when air gets hot, and smoke dampers close on a signal from the fire alarm. Damper position is easy to overlook and is behind many airflow complaints.
Somebody shut the balancing damper on the trunk to stop a noise, now the whole back half of the floor is starved.
Related terms
Economizer
Dampers and controls that bring in cool outdoor air for free cooling instead of running compressors.
VAV
Variable air volume: a system that holds supply air temperature steady and varies the amount of air to each zone.
Test and balance
Measuring and adjusting a building's air and water flows so every outlet, coil and zone gets its design amount.
Register
A supply or return grille fitted with a damper so its airflow can be adjusted or shut off.