CuO--ZnO--CeO.sub.2 catalyst and aged CuO--ZnO catalyst catalytically active for low temperature oxidation of carbon monoxide. The catalysts are co-precipitated, filtered, washed, dried, and calcined. The catalysts can be incorporated into a component of a cigarette or can be used to reduce the concentration of carbon monoxide from a vehicle exhaust emission, a gas used in a laser, a gas used in a fuel cell and/or ambient air undergoing air filtration.