Abstract: An apparatus for treating engine exhaust gases for the effective removal of carbon monoxide, hydrocarbons and/or the oxides of nitrogen from the exhaust system of mobile internal combustion engines. A readily accessible exhaust treating tube in the engine exhaust pipe system contains a removable and disposable open end cartridge which, in turn, contains a fibrous filter which is impregnated with a chemical solution for treating the exhaust gases passing therethrough. The disposable cartridge may be easily replaced at regular intervals by simply removing the spent cartridge and inserting a new one.