Abstract: An improved heating unit comprises a combustion chamber which includes a fuel-supporting perforated burning platform located a distance from the bottom of the combustion chamber. A perforated air plenum is disposed within the combustion chamber a short distance from the combustion chamber top wall to overly a portion of the burning platform. A blower forces air upwardly through the perforations in the burning platform to facilitate waste material combustion and the blower also forces air downwardly through the plenum perforations against the burning platform to further oxygenate the flames and thereby achieve nearly complete combustion. The pressure of incoming air into the combustion chamber forces the exhaust gases through the air passageway above the plenum and out through an exhaust pipe. A heat exchanger, taking the form of a water jacket, surrounds the combustion chamber to cool the combustion chamber and to recover the heat radiated upon combustion of the waste combustible material.