Toxic gas detection is a common issue of interest in domestic as well as industrial environments. There are, in fact, accurate methods to measure gas concentrations (Fourier transform infrared, gas chromatographs, or mass spectrometers) but they are too expensive and require skilled operators. Therefore, these complex detection systems are not useful for many applications, such as hazardous gas level detection in domestic appliances. In this paper, investigations lead to the fabrication of a micromachined tin oxide device for carbon monoxide detection in domestic environments. Relevant parameters that influence gas detection are analyzed and thus the device fabrication process defined by means of microtechnologies. Throughout the material optimization for CO detection, three different additive adding methods by dc sputtering PVD technique are studied and compared for two additives: Pt and Pd.