Recently, there has been an increasing interest in the electronics world for those aspects related to semiconducting gas sensor (SGS) materials. In view of the increasingly strict legal limits for pollutant gas emissions, there is a great interest in developing high performance gas sensors for applications such as controlling air pollution and exhaust gases. In this way, semiconductor gas sensors offer good advantages with respect to other gas sensor devices (such as spectroscopic and optic systems), due to their simple implementation, low cost and good reliability for real-time control systems. In the present work, we have been especially interested in the study of the different ways of metal additive distribution in the most common SGS materials used nowadays and furthermore in the physical and chemical sensing properties they can achieve.