An arrangement at veltilation installations applied to rooms with exhaust air window and being lighted by fluorescent tubes in fittings or fixtures distributed over the ceiling, wherein the passageway for conducting away from the room, the exhaust air being collected adjacent the window surface, is connected to passageways preferably mounted in the ceiling of the room, each of said passageways passing through said fittings of the room for cooling the fluorescent tubes before said exhuast air is conducted away or recirculated to the room via a conditioning unit.