NOVELTY - Reducing gas generator (I) (14) comprises: an oxidant system (30) configured to generate oxidant and provide oxygen content in the oxidant; a merging chamber (32) in fluid communication with the system and a source of a hydrocarbon fuel, where the merging chamber is configured to receive hydrocarbon fuel and oxidant, and to discharge a feed stream containing both the fuel and oxidant; and a reformer (26) configured to receive the feed stream and to reform the feed stream into a reducing gas, and to discharge the reducing gas.    USE - The reducing gas generator is useful: in starting up and shutting down; to perform normal operation of fuel cell (e.g. alkali fuel cells and molten-carbonate fuel); and in piston engines and gas turbine engines.    ADVANTAGE - The reducing gas generator: prevents potential formation of flammable mixture upon mixing with air; and provides reducing gas of variable oxygen content and flammable content, including reducing gas (low strength) to form safe (non-flammable) gas and purging gas with no combustibles and reducing gas (high strength) i.e. high combustible to protect anode from oxidation damage.    DETAILED DESCRIPTION - Reducing gas generator (I) (14) comprises: an oxidant system (30) configured to generate an oxidant having a variable oxygen content from air, and to provide an oxygen content in the oxidant at a selected value from the oxygen content of ambient atmospheric air to greater than that of ambient atmospheric air; a merging chamber (32) in fluid communication with the oxidant system and a source of a hydrocarbon fuel, where the merging chamber is configured to receive the hydrocarbon fuel and the oxidant and to discharge a feed stream containing both the hydrocarbon fuel and the oxidant; and a reformer (26) in fluid communication with the merging chamber which is configured to receive the feed stream and to reform the feed stream into a reducing gas, and to discharge the reducing gas. INDEPENDENT CLAIMS are also included for:    (1) a reducing gas generator (II) comprising an oxidant system configured to provide an oxidant without the use of stored oxygen, and configured to provide an oxygen content of the oxidant having a value that exceeds the oxygen content of ambient atmospheric air, and a reformer configured to receive the oxidant from the oxidant source, to receive a hydrocarbon fuel, to reform the oxidant and fuel into a reducing gas, and to discharge the reducing gas; and    (2) generating the reducing gas, comprising either generating the oxidant having oxygen content greater than that of ambient atmospheric air without the use of stored oxygen, forming the feed stream and reforming the feed stream or generating the oxidant having a selectable oxygen content without the use of stored oxygen, where a maximum oxygen content of the oxidant exceeds that of ambient atmospheric air, and reforming the hydrocarbon fuel with the oxidant to produce the reducing gas.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a fuel cell system having the reducing gas generator.    Fuel cell (12)    Reducing gas generator (14)    Reformer (26)    Oxidant system (30)    Merging chamber (32)