Abstract: Disclosed is a means for heating a space with hot air comprising essentially first and second enclosures, the second enclosure being completely surrounded by and spaced apart from the first enclosure to form an air chamber for the circulation and heating of air. Energy for heating the air is supplied by burning fuel (wood, coal, etc.) disposed on a plurality of spaced apart, grate forming, tubelike members lying in a common plane positioned inside of the second enclosure. A terminal portion of one end of the tubes bridge across the air chamber and the tubes terminal edges are exposed to the space sought to be heated; terminal edges of the other end of the tubes are exposed to and communicate with the air chamber.