The WO3 nanowires (NWs), fabricated on a commercial Al2O3-based sensor platform, underwent near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) analysis during ethanol detection. Our findings revealed challenges that may appear in utilizing NAP-XPS studies for studying a real gas sensor in operando conditions. Through NAP-XPS analysis, we explored the gas-sensing mechanisms of pristine and Pt-decorated WO3 NWs for ethanol sensing at different temperatures, demonstrating a combination of several mechanisms commonly observed in metal-oxide chemiresistors. For ethanol sensing, the primary driving force for the sensor's macroscopic electrical response at low temperatures was the adsorption of ethanol molecules. Conversely, at high temperatures, it involved the adsorption of ethoxy groups along with the reducing effect of ethanol on the WO3 surface. It is shown that the surface oxygen vacancies play a crucial role in the ethanol sensing mechanism of WO3 NWs-based gas sensors. Figure 1