NOVELTY - An input gas stream is contacted with a preferential oxidation catalyst for selectively oxidizing carbon monoxide. The catalyst comprises (in weight%) an oxide support (at least 50), such as activated alumina, zirconia, titania, silica, zeolite and/or zinc oxide dispersed with copper or its oxide, platinum group metal (0.01-0.5) and reducible metal oxide.    USE - For removing carbon monoxide in hydrogen feeds streams supplied to fuel processes, particularly to proton exchange membrane fuel cells, used in residential or vehicular applications.    ADVANTAGE - The catalyst achieves higher carbon monoxide conversion at low temperatures than conventional copper based catalyst. The improved catalytic activity at low temperature allows the catalyst to operate at low temperatures where the selectivity for carbon monoxide oxidation over hydrogen oxidation is thermodynamically more favorable. The improved carbon monoxide selectivity at low temperatures allows achievement of low levels of carbon monoxide in the output gas stream. The use of a base metal, such as copper, in the catalyst offers significant cost advantages over platinum based preferential oxidation catalysts. The catalyst can be in any form including tablets, extrudates, wash coat compositions deposited on monolith substrates and high strength, high heat capacity particulate catalysts.    DETAILED DESCRIPTION - An input gas stream comprising carbon monoxide, oxygen and hydrogen is contacted with a preferential oxidation catalyst for selectively oxidizing carbon monoxide. The catalyst comprises (in weight%) an oxide support (at least 50), such as activated alumina, zirconia, titania, silica, zeolite and/or zinc oxide. Copper or its oxide, platinum group metal (0.01-0.5), such as platinum, palladium, rhodium, osmium, iridium and/or ruthenium and reducible metal oxide, such as oxides of chromium, vanadium, molybdenum, cerium, praseodymium, neodymium, titanium, nickel, manganese, and/or cobalt, are dispersed on the support.    An INDEPENDENT CLAIM is included for a method of removing carbon dioxide from an input gas stream.    DESCRIPTION OF DRAWING(S) - The figure shows the drawing of fuel processor unit for supplying hydrogen to a fuel cell.