NOVELTY - Selective oxidizer assembly (12) contains a fuel gas inlet (16), a metered oxygen or air inlet (18), a flow section (I) of catalyzed fuel gas and oxygen, a coolant inlet (22), and a heat exchange section (I) which includes monolithic open cell foam component (MOCFC) which is in contact with coolant fluid conduit. MOCFC includes a lattice which provides enhanced heat transfer from gas flowing through MOCFC.    USE - Used for fuel cell power plant.    ADVANTAGE - The use of heat exchanger elements and open cell monolithic construction, with its minimized gas flow surface area and excellent heat transfer characteristics, allows minimization of size and weight of selective oxidizer assemblage. Therefore, light weight, sturdy selective oxidizer assemblage which provides large surface area per unit volume of the selective oxidizer, and efficient heat transfer properties is provided. The compact selective oxidizer assemblage is desirable for vehicular applications and also benefits larger higher power output fuel cell power plants or stand-alone selective oxidizers.    DETAILED DESCRIPTION - Hydrocarbon fuel gas selective oxidizer assembly comprises (i) fuel gas inlet to direct a mixture of fuel gas into the assembly, (ii) metered oxygen or air inlet, (iii) flow section (I) of catalyzed fuel gas and oxygen connected to fuel gas inlet to provide enhanced gas mixing flow pattern for fuel gas flowing through the flow section, (iv) coolant inlet to direct coolant fluid into the assembly so that the coolant is operable to absorb heat from each of the sections in the assembly, and (v) heat exchange section (I) which is connected to the coolant inlet. The heat exchange section (I) provided adjacent to flow section (I) of catalyzed fuel gas and oxygen, includes MOCFC which is in contact with at least one coolant fluid conduit. MOCFC includes a lattice portion which provides enhanced heat transfer from the gas flowing through MOCFC. The coolant fluid conduit absorbs heat from the lattice. An INDEPENDENT CLAIM is also included for heat exchange assembly comprising MOCFC which is in contact with at least one coolant conduit.    DESCRIPTION OF DRAWING(S) - The figure shows the schematic, fragmented perspective view of selective oxidizer assemblage.    Selective oxidizer assemblage (12)    Fuel gas inlet (16)    Air inlet (18)    Coolant fluid inlet (22)    Plates (40,42)