Abstract: The distribution-pressurized natural gas is supplied via a conduit arranged in the piston of an electrovalve in a nozzle of which the outlet leads to a cone which provides, with the nozzle, a ring-shaped opening which, connected to the atmosphere, acts as a secondary nozzle for injecting air into the gas flow. The cone is followed by a cylindrical element then by an abrupt widening section which opens into a heat exchanger which is in contact with a substrate impregnated with a catalytic material which oxidizes fuel gas. A small amount of air is sucked up by the widening and mixed with the gas. This mixture is then treated in the exchanger up to the transformation temperature of the sulphur-containing compound and the sulphur is then oxidized.