Abstract: The diffuser has outwardly flared lower side walls and an upper vertical wall portion adapted to receive primary air from a supply source. The vertical portion includes a lower extension into the space defined by the lower flared side walls, and the lower extension includes vertically elongated horizontally oriented orifice openings at horizontally spaced positions therein. A damper device is provided which is adjustably positionable at different elevation positions and operable to vary the open area of the elongated orifice openings by variably masking and unmasking said openings. The air flow through the orifice openings is effective to provide induced flow of secondary air from the room.

Abstract: A primary fluid nozzle induces secondary fluid flow through an induction port opening. A damper valve element is provided at the induction port and is constantly biased open. A variable flow fluid inlet is positioned to one side of the nozzle orifice and arranged to direct fluid against the induction port damper tending to close the damper depending upon the flow of fluid through the variable flow fluid inlet. Thus, when primary fluid flow increases through the variable flow inlet, the secondary fluid damper tends to be closed, reducing secondary fluid flow.