The gas sensing characteristics of several favorable metal oxide semiconductors, such as ZnO, In2O3, SnO2, and WO3, under various irradiation conditions, utilizing ultraviolet light emitting diodes (UV-LED), were investigated. The morphology and structure of sensing materials prepared by precipitation route were analyzed, and the sensors’ performances were evaluated against low concentrations of NO2. In particular, the effects of several UV source-related operating parameters, such as irradiation wavelength, irradiance, and irradiation pattern, were studied, and the underlying mechanism for the adsorption/desorption kinetics of gas molecules under different UV irradiation was demonstrated. The effect of radiation specifications was found to play an essential role in the response of the sensors. Thus, appropriate conditions must be applied to the design and operation of the UV-LED activated gas sensors for optimal performance.