a method is provided for oxidizing gases such as , for example , co , aldehydes having carbon atoms in the range 1 to 5 , ketones having carbon atoms in the range 3 to 5 , and alcohols having carbon atoms in the range 1 to 5 , wherein the gas at a relative humidity in the range 0 to 100 % and an input temperature in the range - 50 ° to 150 ° c . is contacted with a catalyst assembly comprising a hydrophobic support having a surface area in the range 50 to 1 , 500 m 2 / g and selected from the group consisting of silicalite , silylated silica , and styrene divinylbenzene polymers , and , on said support a catalytically active metal selected from the group consisting of chromium , molybdenum , tungsten , manganese , rhenium , iron , ruthenium , osmium , cobalt , rhodium , platinum , iridium , nickel , copper and silver , said metal being present in an amount in the range 0 . 1 to 22 wt % of the total weight of the catalyst assembly . the catalyst assemblies used are generally catalytically active in the presence of liquid water and water vapor for longer periods than known catalyst assemblies and function at ambient temperatures .