The progress of mankind can be seen, from a certain point-of-view, as a continuous effort of the human being to reproduce himself artificially in order to reduce his physical fatigue and to make himself more powerful. The most recent gigantic advances in his capability to elaborate signals and actuate actions mechanically seem to reward such a desire. However, robots still have problems in emulating the senses of taste and smell because of the impracticability in using traditional chemical analysis methodology to implement chemical sensors. That is why it makes sense to go deeper into the study of electric and ionic conduction in solids to detect gases. Possible mechanisms to be exploited take advantage of Nernst cells, and very recently a hydrogen sensor operating at room temperature has been developed for perspective applications in advance warning of possible earthquakes. A second possible mechanism deals with the high-temperature semiconductor-like properties of certain oxides, even if in such a case the gas selectivity and long-term sensor stability require improvement. Thirdly, MOSFET devices having a metal gate layer that selectively absorbs gases are under development.