Abstract: An apparatus for producing oxygen-free combustion gases, comprising a combustion chamber provided with a cooling jacket or shell and wherein liquid or gaseous hydrocarbons are burnt with combustion air and subsequently cooled through spray cooling by water introduced through nozzles into the rear portion of the combustion chamber, whereupon secondary cooling and scrubbing take place within a secondary cooling zone subsequent to the plenum chamber of said combustion chamber and provided with a plurality of gas outlet ports. That spray heads are arranged in the region of said gas outlet port(s), to produce a spray stream or jet directed to said outlet ports. A chamber is connected to said outlet port which chamber is surrounded by a wall provided with at least one gas outlet port, with the stream or jet of said spray heads being aligned with said gas outlet ports.