An apparatus for oxidizing volatile organic compounds from an electrographic printer may comprising a) a printer system that vents a gas stream containing volatile organic compounds to a first inlet; b) a first mast transfer element transmitting the gas stream to a catalytic treatment system, c) The catalytic treatment system comprising separate contact sections for an unsupported catalyst and a supported catalyst; a diverter system that can direct the gas stream along paths selected from the group consisting of to the unsupported catalyst only, to the supported catalyst only, first the unsupported catalyst and then the supported catalyst, and the supported catalyst and then the unsupported catalyst.