Gas sensors based on semiconducting metal oxides were coated with catalytic membranes to improve the selectivity of gas detection. CuO was used to establish a catalytic membrane to develop an active gas filter. The coated gas sensors were tested for their gas-detecting properties by exposure to model gas atmospheres. The catalytic effect of the membranes was examined by analyzing the composition of the gas atmosphere with an FT-IR spectrometer during exposure. To test the discrimination power, eight sensors with and without coating were combined in an array which was exposed to a mixture of two gases. A good selectivity was demonstrated using principal component analysis (PCA).