We demonstrate that conductometric gas sensing at room temperature with SnO2 nanowires (NWs) is enhanced by visible and supraband gap UV irradiation when and only when the metal oxide NWs are decorated with Ag nanoparticles (NPs) (diameter < 20 nm); no enhancement is observed for the bare SnO2 case. We combine the spectroscopic techniques with conductometric gas sensing to study the wavelength dependency of the sensors’ response, showing a strict correlation between the Ag-loaded SnO2 optical absorption and its gas response as a function of irradiation wavelength. Our results lead to the hypothesis that the enhanced gas response under UV–vis light is the effect of plasmonic hot electrons populating the Ag NPs surface. Finally, we discuss the chemiresistive properties of Ag-loaded SnO2 sensor in parallel with the theory of plasmon-driven catalysis, to propose an interpretative framework …