The DSQW rectangular multi-blade dampers can be used to control and isolate air flow in rectangular ductwork. Rectangular multi-blade dampers is made of plastic. The DSQW damper can have a hand-operated damper mechanism, an externally-mounted actuator, or an actuator mounting. The damper mechanism is installed on the outer surface of the housing. The damper blade rotation mechanism features short and long shafts rotating by intermeshed gears installed on bearings. The gears are installed on the outer surface of the housing.