NOVELTY - Fuel-cell electromotive-force reduction factor components and sulfur compounds contained in air are removed, and the sulfur-compound concentration is set to 5 ppb or less.    USE - Used for purifying air used for fuel cells (claimed), such as polymer electrolyte fuel cells, aqueous-alkali-solution electrolyte-type fuel cells, phosphoric-acid aqueous-solution electrolyte-type fuel cells, molten carbonate electrolyte-type fuel cells, or solid-acid compound electrolyte-type fuel cells, used for electric-power generation in vehicles.    ADVANTAGE - The process enables the supply of pure air to fuel cells by efficiently removing the electromotive-force reduction factor components and sulfur compounds, which enables stable maintenance of fuel-cell characteristics over a long period of time and improves the durability of the fuel cell. The polyurethane foam has low pressure-loss and excellent contacting efficiency with air.    DETAILED DESCRIPTION - The sulfur compound is sulfur dioxide, sulfur trioxide, and/or hydrogen sulfide. Adsorbent particles of activated charcoal, wood activated carbon, petroleum pitch group ball-shaped activated charcoal, pellet-form molded activated charcoal, natural or synthetic zeolite, activated clay, surface-active agent, cation or anion exchange resin, cation or anion exchange fiber, chelate resin or compound, inorganic cation or anion adsorption agent, and/or inorganic synthetic deodorant are used as the substance for decomposing or adsorbing the electromotive-force reduction factor components. The adsorbent particles are held by a three-dimensional network-skeleton structure through a binder layer. The structure is polyurethane foam, preferably polyether group polyurethane foam. The binder is polyether group urethane binder.    INDEPENDENT CLAIMS are included for the following:    (1) an air purifier; and    (2) a fuel cell.    DESCRIPTION OF DRAWING(S) - The figure shows the logarithmic graph of the relationship of sulfur-dioxide concentration in cathode supply air, and voltage-reduction speed of fuel cell. (Drawing includes non-English language text).