Used to control air volume in circular air ducts. Manually controlled volume dampers are adjusted manually to the air volume requires and the locking mechanism on the handle is used to maintain the specified level of air. On request, they can be manufactured to incorporate 24V and 240V servo-motor control. Dependent on operational requirements, the blades in the air dampers can be manufactured from Ø5 mms perforated sheet metal, handle mechanism from injection moulded PVC.