Semiconductor gas sensors (typically SnO2, TiO2, WO3, LaFeO3 and solid solutions of them) represent a modern sensing technology based on solid-gas interaction. These sensors can detect a vast selection of gases and vapors, even at extremely low concentrations (in the range of ppb). In the recent years, many research and studies on the electrical transport properties of these semiconducting nanostructures triggered a significant progress in this technology. MIST E-R – its unit at University of Ferrara, develops synthesis techniques for sensing materials, fabricates individual sensors and complete monitoring systems that can satisfy the requirements of the individual customers. Major advantages of semiconductor gas sensors technologies over conventional instrumentation based on optical methods are ultra-high sensitivity, compact size and low cost as well as radical reduction of maintenance requirements and possibility of remote control. This technology has multiple applications, just to mention a few of them: water and air monitoring against main pollutants (CO, VOCs, NOx, benzene, O3 etc.), detection of (toxic) gases in industrial plants, leakage detecting and many more.