Environmental Pollution is a global issue. Over the last decade the demand for accurate and dedicated sensors to provide precise value of species to be monitored and control the environmental pollution have accelerated efforts for the development of new sensing material and technologies. The most important, hazardous and very common pollutant gases are CO and CO2, H2, which are produced partly by natural decays, and more by industries and other man made burning processes. SnO2, is the most extensively studied oxide while Al2O3, BaTiO3. The other oxides like ZnO, ZrO2, TiO2, MoO2, MnO3, Fe2O3,...