Abstract: A waste disposal system for the combustion of waste materials which includes a combustor having an inlet end and an outlet end with a furnace enclosing the outlet end. A step extends out from the back wall of the furnace which is spaced from and below the combustor outlet end. The step is hollow on the inside to form a plenum chamber to receive air and has an upper surface which defines a plurality of openings into the furnace whereby air injected through the openings deflects airborne ash and combustible solids from the outlet end of the combustor up into the furnace.