Supply Air device (1) for controlling supply air flow to a building space, comprising a chamber (2) having a supply air inlet (3) and an air outlet (4). A first tube (10) in the chamber is connected at an open first end (11) to the supply air inlet, wherein the first tube has a side wall (13) which is permeable to air. A throttle member (30) is slidably connected to the first tube to change a degree of exposure of the side wall to control air flow through said side wall to the outlet. The exposable side wall comprises a layer of porous material (14) through which air is discharged.