Abstract: An air ionizer for installation in the air intake path of an internal combustion engine, to introduce ozone and other oxidizing agents into the engine with acceptable levels of air flow restriction and at a sufficient concentration level to substantially improve combustion within the engine. A glass tube is filled with an inert gas and has an inner electrode extending a short distance into an end of the tube. A foraminous copper outer electrode substantially surrounds the glass tube and is slightly spaced apart from it. A high voltage is applied between the inner and outer electrodes, so that when air flows past the tube, ozone and other oxidizing agents are generated between the outer surface of the tube and the outer electrode, and escape into the air stream through the holes in the outer electrode.