NOVELTY - Providing an improved catalyst and selective oxidizer bed regeneration process that employs systems that are much lighter in weight than prior art systems and less complex in design and cheaper to manufacture, operate and maintain.    USE - A method and apparatus for selectively oxidizing the carbon monoxide present in a mixture of gases, including hydrogen, carbon dioxide and water vapor. It is useful in automotive applications.    ADVANTAGE - The method counteracts the poisoning effects of the selective oxidation catalyst active sites by carbon monoxide, to maintain the concentration of carbon monoxide in the outlet gas stream well below 10 ppm and to periodically regenerate the selective oxidizer bed.    DETAILED DESCRIPTION - Regenerating a selective oxidizer bed, comprises:    (a) providing a fuel processor system;    (b) providing a selective oxidizer bed;    (c) heating the selective oxidizer bed to 82 degrees C passing oxygen containing gas through the selective oxidizer bed while maintaining the bed at this temperature for a selected period of time;    (d) purging the selective oxidizer bed with inert gas or steam to remove residual oxygen containing gas; and    (e) introducing hydrogen rich stream from the fuel processor system into the selective oxidizer bed.    An INDEPENDENT CLAIM is also included for a carbon monoxide reactor for a fuel cell, comprising:    (i) a single selective oxidizer bed having an input and an output port, the output port being connected to a fuel cell;    (ii) a fuel processor connected to the input port of the selective oxidizer bed, the fuel processor providing fuel into the selective oxidizer bed;    (iii) heat control means provided in the single selective oxidizer bed for controlling the temperature thereof; the selective oxidizer bed being maintainable at 82 degrees C; and    (iv) an oxidant source connected to the input port of the selective oxidizer bed, the oxidant source being capable of providing oxygen into the selective oxidizer bed via the input port while the selective oxidizer bed is at a temperature of 82 degrees C.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of a selective oxidizer apparatus as used for treating hydrogen rich fuel for a fuel cell device.    Selective oxidizer bed (20)    Fuel processor (11)    Fuel cell device (12)    Anode side (13)    Cathode side (14)    Fuel supply conduit (15)    Oxidant supply conduit (16)    Discharge conduit (17)