Abstract: The blower unloading or air volume control device is for use with an air blower assembly having a fan wheel or impeller assembly mounted for rotation about the rear orifice in the air inlet funnel. The device comprises a moveable air deflecting member or cone aligned axially with the blower assembly inlet funnel for varying the entrance dimension to the impeller blades and for sealing the rear inlet funnel orifice. A mounting structure is fixed to the blower assembly for supporting the air deflecting cone. A linear movement mechanism operative on the air deflecting cone is provided to vary the stroke of the air deflecting cone based on pressure differential demands in the system serviced by the blower assembly. The air deflecting cone is movable from a position in the impeller assembly cavity to engage the rear orifice of the inlet funnel to control the air volume throughput and to, thereby, control the operating efficiency of the air blower assembly.