Circular constant air volume dampers The SKC-C series dampers are designed to facilitate balancing of ventilation systems. Damper suitable for circular duct mounting. Those dampers maintain the constant air volume at varying pressures, caused by connection and disconnection of system parts, clogging of filters and ducts, wind effects, window opening etc. SKC-C is an automatic damper independent of external energy sources. This operation is based on the balance of forces on the blade between the air pressure and the reactive forces that exert a spring and a inflatable damper. The adjustment knob has a graduated rate scale allows quick and easy adjustment of the desired air flow. Each nominal size damper allows a selection of flow with a ratio Vmax Vmin 3:1.