A method for treating an effluent gas from a semiconductor processing system includes the steps of exhausting the effluent gas from a processing chamber, and catalytically treating the effluent gas with the at least one mixed metal oxide. The effluent gas includes unconsumed process gasses introduced during semiconductor processing operations, such as during chemical vapor deposition (CVD) and plasma-reactive ion etching. The mixed metal oxide may include a hetero bi-metal oxide, a hetero tri-metal oxide, or a perovskite. A hetero bi-metal oxide includes LaCoO3 and LaMnO3, for example, and a hetero tri-metal oxide includes (LaxPr1−x)CoO3 and (LaxPr1−x)MnO3, for example. The effluent gas may include at least carbon monoxide and/or ozone. Thus, catalytically treating the effluent gas preferably includes the catalytically converting carbon monoxide to carbon dioxide and/or ozone to oxygen. With the effluent gas being treated by the catalytic converter prior to being released into the atmosphere, undesirable gases, such as carbon monoxide and unreacted ozone are efficiently converted into non-harmful carbon dioxide and oxygen.