Abstract: Variable flow of either primary air or of a mixture of primary and secondary air is provided to an enclosure by an air diffuser adapted for installation in an opening in the enclosure. Sleeve means is movably mounted within a housing of the air diffuser for movement between a closed position in which apertures of the housing are closed by the sleeve means and an open position in which they are open. Actuator means is engageable with the sleeve means for selectively moving the sleeve means between the closed and open positions and to positions therebetween so as to discharge a desired proportion of primary air through the apertures into a plenum to bypass the enclosure. Deflecting means is mounted on the housing for deflecting the primary air outwardly as it is discharged into the enclosure. The sleeve means may extend downward toward the deflecting means such that a passage of variable area is formed to further direct the primary air through the apertures.

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.