NOVELTY - Method comprises: passing a gas that includes a gas phase contaminant through a catalytic membrane reactor (100) at a temperature of 150-300 degrees C; and oxidizing the gas phase contaminant with an oxidative catalyst layer for reducing a concentration of the gas phase contaminant in the gas. The catalytic membrane reactor includes a bundle of tubular inorganic membranes.    USE - The method is useful for removing gas phase contaminants (such as a non-methane organic compound (e.g. halogen-containing compounds and sulfur-containing compounds) or chemical warfare compound e.g. sarin, cyanogen chloride and tabun) from gas (such as a landfill gas, a biogas or breathing air) by catalytic oxidation.    ADVANTAGE - The method allows simple, rapid and continuous removal of the gas phase contaminants with less labor intensive and reduced equipment consumption in an environmentally friendly manner.    DETAILED DESCRIPTION - Method comprises: passing a gas that includes a gas phase contaminant through a catalytic membrane reactor (100) at a temperature of 150-300 degrees C; and oxidizing the gas phase contaminant with an oxidative catalyst layer for reducing a concentration of the gas phase contaminant in the gas. The catalytic membrane reactor includes a bundle (108) of tubular inorganic membranes. Each of the tubular inorganic membranes comprises a macroporous tubular substrate with the oxidative catalyst and a microporous layer disposed on a bore side of the macroporous tubular substrate. At least 50% of the gas flows through the tubular inorganic membranes in a Knudsen flow regime. An INDEPENDENT CLAIM is included for a system comprising the catalytic membrane reactor comprising a heating element in thermal communication with the bundle of tubular inorganic membranes and a housing (102) having a gas inlet (104) and a gas outlet (106) and containing the bundle of tubular inorganic membranes, where the catalytic membrane reactor is configured such that a gas flows into the housing through the gas inlet, into a bore of the tubular inorganic membranes, through a wall of the tubular inorganic membranes, and out of the housing through the gas outlet.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of a catalytic membrane reactor for catalytic removal of gas phase contaminants.    Catalytic membrane reactor (100)    Housing (102)    Gas inlet (104)    Gas outlet (106)    Bundle of tubular inorganic membranes. (108)