Abstract: A room air conditioning apparatus for exchanging heat and/or moisture between fresh atmospheric air entering the room from the outside and consumed air being discharged from the room combines high capacity with relatively small dimensions, low air velocities and small pressure drops so as to minimize generation of disturbing noise. Within a casing, a motor-driven regenerative-type rotor passes through two air stream zones in the first of which is a motor-driven fan for discharge of consumed room air into the outer atmosphere and in the second of which is a motor-driven fan for supply of fresh air to the room from the outer atmosphere. In the rotor, the two air streams exchange heat and/or moisture content so that the supply of fresh air is given a desired, predetermined temperature and a desired moisture content.