Abstract: A forced air, fuel burning heater is provided which includes a relatively large damper plate slideably mounted immediately below the top wall of the heater, to thereby insulate the top wall from the heat of combustion and thereby reduce the temperature and thus the tendency of the top wall to warp from excessive heat. The damper plate preferably includes a rearward edge which is doubled upon itself to further insulate the edge of the flue opening in the top wall from heat, where warpage commonly occurs. The disclosed heater also includes a separate blower assembly which may be selectively mounted on either side of the combustion chamber with equally effective air circulation, and the hearth plate includes an upwardly inclined forward edge portion for reflecting radiant heat back toward the heater and thus reducing the temperature of the adjacent floor surface.