TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Device: The device further comprises a catalyst disposed on a portion of the reaction chamber. It also comprises a sensor disposed downstream of the combustor and controller responsive to a signal sent from the sensor. It also comprises a pressure source in pressure communication with the second reactant. It also comprises a cathode exit valve configured to control back-pressure in a portion of the cathode flowpath. The reaction chamber comprises first and second reactant conduits. It also comprises a power conversion mechanism configured to take electricity generated by the fuel cell system and converts it to motive power. It comprises a vehicle configured to house the fuel cell system and the power conversion mechanism. It is configured such that the first and second reactants are introduced in counterflow relation to one another. The combustor is a catalytic combustor. It is a thermal mass that heat generated by a reaction between the first and second reactants is absorbed by the combustor, thus keeping temperature increases concomitant with the reaction below a predetermined amount of up to 20degreesC. The fuel cell is a proton exchange membrane fuel cell. Preferred Method: The adjusting step comprises opening the inerting valve, thus causing the introduction step to effect a reduced voltage potential in the anode and the second adjusting steps comprises closing the run valve one the reduced voltage potential has been attained. The reduced voltage potential is up to 0.5, preferably up to 0.4 volts.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The first reactant is hydrogen-rich fluid. The second reactant is oxygen-rich fluid, e.g. air.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The first reactant is methanol, hydrogen, methane or gasoline.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The first reactant is hydrogen-rich fluid. The second reactant is oxygen-rich fluid, e.g. air.