The odorous components of sewage gas consist mainly of ca. 15-40 ppm hydrogen sulphide. The gas may also contain methane. The catalytic combustion of hydrogen sulphide and methane has been studied using palladium- and platinum-based monolithic catalysts. Platinum-based catalysts perform better in the presence of hydrogen sulphide and kinetic equations have been derived. The relationships were used to design an industrial converter, which has operated satisfactorily for two years.