NOVELTY - Carbon monoxide (CO) in a reformate stream is selectively oxidized by passing a fuel stream comprising hydrogen and carbon monoxide into a reaction chamber (1) that contains catalyst (2) to selectively promote oxidation of the CO to carbon dioxide in the presence of hydrogen; supplying an oxygen-containing stream into the reaction chamber; and periodically interrupting flow of oxygen-containing stream into the reaction chamber.    USE - Oxidizing carbon monoxide in a reformate stream of fuel cell of electric motor vehicle.    ADVANTAGE - The process oxidizes the carbon monoxide that continues to function at high capacity, thus achieving effluent concentrations of CO at less than 50 ppm-vol. It also maintains the production of hydrogen while reducing the CO levels below a level that interferes with fuel cell anode operation.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (a) an apparatus for carrying out this method comprising:    (i) a primary reaction chamber having a primary catalyst bed for promoting oxidation of CO to carbon dioxide, an inlet (4) for directing the fuel stream through the primary catalyst bed, and inlet (5) for directing an oxygen-containing stream through the primary catalyst stream;    (ii) flow controller for interrupting the oxygen-containing stream flowing into the primary reaction chamber; and    (iii) an outlet (10) from the primary reaction chamber; and    (b) a process for the generation of a hydrogen-rich fuel gas stream for use in a fuel cell for the generation of electric power, comprising:    (i) passing a feed stream to a fuel processor comprising an integrated reforming and water gas shift conversion zone to produce a fuel stream comprising hydrogen, CO, carbon dioxide and water;    (ii) passing the fuel stream at 70-160 degrees C in the presence of an oxygen-containing stream to a preferential oxidation zone containing a preferential oxidation catalyst to produce the hydrogen-rich fuel gas stream;    (iii) interrupting the oxygen-containing stream to maintain the CO below a desired level; and    (iv) passing the hydrogen-rich fuel gas stream to a fuel cell for the generation of electric power and withdrawing electric power.    DESCRIPTION OF DRAWING(S) - The figure is a schematic view of the reaction chamber.    Reaction chamber (1)    Catalyst (2)    Inlet (4, 5)    Heat exchange zone (7, 8)    Carbon monoxide level sensing element (9)    Outlet (10)