The sensing properties of WO 3 -based gas sensors were evaluated at an operating temperature of 150 °C in the presence of different volatile organic compounds (VOCs). Simultaneously to the sensing tests, operando diffuse-reflectance infrared Fourier transform spectra were acquired. Remarkably, no CO 2 generation was observed under gas exposure for any of the target VOCs. Catalytic combustion properties of the WO 3 toward acetone and ethanol at temperatures from 150 to 400 °C, both in dry and humid atmospheres, were additionally performed. Such measurements confirmed that no combustion occurred for ethanol (up to at least 300 °C) while it became detectable for acetone only starting from 250 °C. The reaction products are acetaldehyde and acetate in the case of ethanol exposure and acetate and formate in the case of acetone exposure. The oxidation catalytic effect of WO 3 was confirmed for both toluene, where benzaldehyde and benzoate modes were observed, and acetylene (where acetaldehyde and ethenol were detected). The systematic absence of CO 2 as a product and the identification of oxidized species are the basis of the proposed reaction mechanisms.