TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Component: The damper is rotatably disposed in the gas outlet. An air injection apparatus is provided in communication with the air inlet, and has a speed control (14) for controlling the volume of air injected. The air inlet is provided with restrictions defining a labyrinth. A secondary air combustion zone is provided in the gas outlet to the chamber. A heat recovery boiler is provided in communication with the gas outlet of the chamber. A fan is provided in communication with the gas outlet for inducing a draught in the outlet. The chamber is defined by walls and configured to redirect heat radiation to the material on the conveyor. The wall is arranged in a concave configuration to direct heat radiation to the material. The material inlet has air seal(s) to prevent ingress of air into the chamber.    TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: The determined pressure is compared to a pre-selected pressure range and if it is outside the range the volume of air introduced into the chamber through the air inlet is increased or decreased accordingly. The pressure within the chamber is controlled to effect the amount of air that is drawn into the chamber. It is controlled by controlling the flow of exhaust gas in the outlet. The flow of exhaust gas is controlled by a movable restrictor in the outlet. The air is controllably injected into the chamber during the thermal treatment. Air is controllably injected by controlling the speed of air injection apparatus. Heat radiation is redirected from the combusting gas to the material in order to increase the rate of degradation of the material. The heat is redirected by making at least one walls of the chamber reflective. The thermal degradation process is gasification, or combustion. The gas emitted from the material is combusted above the material in order to radiate heat to the material and to sustain gasification or combustion without a source of external heat.