TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The microporous layer has a thickness of 1-10 mu m, a porosity of 25-50%, an average pore size of 4-50 nm. The system further comprises: an adsorption bed upstream or downstream of the catalytic membrane reactor; a photo-oxidation reactor upstream or downstream of the catalytic membrane reactor; a particle filtration unit disposed downstream of the photo-oxidation reactor; a selective surface flow reactor upstream or downstream of the catalytic membrane reactor; and an adsorption bed downstream of the catalytic membrane reactor and the selective surface flow reactor. The photo-oxidation reactor comprises a gas flow path and UV source arranged relative to the gas flow path to allow for UV irradiation of the gas contained in the gas flow path. The oxidative catalyst is impregnated in the microporous layer, and is present in a layer disposed between the microporous layer and the macroporous tubular substrate. The selective surface flow reactor is upstream of the catalytic membrane reactor.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: A pressure drop across the bundle of tubular inorganic membranes is 2-4.5 inches of water. The method further comprises: removing at least some of siloxane before passing the gas through the catalytic membrane reactor; condensing at least some of chemical warfare compounds into a liquid phase in a selective surface flow reactor for reducing a concentration of the chemical warfare compounds in the gas; and passing the gas through an adsorption bed that is downstream of the selective surface flow reactor and the catalytic membrane reactor. The step of removing the siloxane involves exposing the gas to UV radiation to form silica particles, and further comprises filtering the silica particles from the gas before passing the gas through the catalytic membrane reactor. Preferred Components: The gas comprises methane. The gas phase contaminant is a non-methane organic compound or a chemical warfare compound. The gas phase contaminant further comprises a siloxane.