A system has a fuel cell. The fuel cell has a source of hydrogen and a source of oxygen containing gas. The hydrogen is connected for passage across the anode. The source of oxygen containing gas is connected to pass across a cathode. The fuel cell produces electricity. A catalytic oxidizer oxidizes hydrogen within the system. A cooling water circuit passes across cooling water passages in the fuel cell and cools the cathode. Cooling water downstream of the cooling water passages passes across the catalytic oxidizer to heat the catalytic oxidizer. An enclosed vehicle is also disclosed.