SnO2 is Pd doped by using two different methods. In the first method, SnO2 and PdCl2 powders are simply mixed in a mixer, then cold pressed and sintered at high temperature. In the second one, a fixation method is used: a PdCl42− complex is chemically fixed on the surface of the SnO2 powder, the fixed species subsequently being reduced to metallic Pd; powder is then cold pressed and sintered at 650°C. Pd dispersion is lower in the case of the mixing method, but electrical properties are about the same for the two kinds of sensors realized by Coreci Company. On the one hand, CH4 and aliphatic hydrocarbons are selectively detected at high temperature (400-450°C). On the other hand, CO detection is possible at low temperature (50°C, for example). Nevertheless, response time is long and can be improved by two different working modes: continuous pulsed temperature plus cleaning pulse, or isothermal measurement plus cleaning pulse. By doing this, the CO sensitivity is greatly increased, and the humidity variations are easy to compensate. However, the use of a carbon-based filter is necessary in order to avoid the presence of NOx which is a great interferent. These two kinds of sensors call be used either as a domestic alarm in order to control CH4 or CO leaks, or as a control sensor in order to monitor car pollution.