TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Component: The contaminant removal system further includes a water injection device (70) disposed to inject water into the flow of inlet air to provide moisture to enhance the dissolution of water-soluble contaminants from the inlet air. The cleansing arrangement comprises a scrubbing apparatus; a water supply circuit flowing through the apparatus; and a mass transfer device. The fuel cell power plant (110) includes a water coolant circuit having a water treatment system, and a water recovery device. The degasifying apparatus has an outlet connected to the hydrogen generator for supplying the cleansed air. A supply of oxidant reactant is required for the CSA, and the cleansed air is connected (138', 37) to the CSA to supply the oxidant reactant.Preferred Condition: The degasifying apparatus is structured such that the inlet air admitted to it is, on a time and area basis, in intimate contact with the water coolant circulating through it, to dissolve water-soluble contaminants from the inlet air. The inlet air is connected to flow through the mass transfer device and to the degasifying apparatus.Preferred Function: The inlet air is connected to the scrubbing apparatus for intimate contact with the water flowing through it, to dissolve and remove water-soluble contaminants from the inlet air for the hydrogen generator; or to the degassing apparatus for removal of contaminants from the inlet air to provide cleansed air. The reactant exhaust(s) is connected (144) to flow through the mass transfer device counter to the flow of the inlet air to enhance the dissolution of water-soluble contaminants from the inlet air. The CSA receives the cleansed stream of oxidant and discharges spent oxidant containing moisture. The spent oxidant and the stream of inlet oxidant are passed in counter-current relation through the water recovery device to transfer moisture from the spent oxidant to the stream of inlet oxidant to facilitate the dissolution of water-soluble contaminants prior to passing the inlet stream of oxidant to the accumulator/degasifier.Preferred Product: The CSA produces humid reactant exhausts of oxidant and reducing agent.Preferred Device: The hydrogen generator is a catalytic hydrogen generator for a fuel cell assembly in a fuel cell power plant comprising a coolant loop having coolant flowing through an accumulator/degasifier.Preferred Method: The method of removing water soluble contaminants from a stream of inlet oxidant further comprises directly injecting water into the stream of inlet oxidant to provide moisture to enhance the dissolution of water-soluble contaminants from the inlet oxidant.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The supply of oxidant is inlet air. The contaminants include sulfur, including sulfur compounds.