Abstarct: Developing new methods and techniques for quality control of food products is critical because providing healthy and quality food is essential for humans. Gas sensors can monitor all processes attributed to food production and storage. In this regard, gas sensors baxsed on nanostructures were fabricated for application in the food industry. ZnO nanoparticles as sensing materials have been synthesized by the hydrothermal method in different conditions. Gas sensors baxsed on ZnO were fabricated to detect two important gases (ethanol and carbon dioxide) in the food industry. In order to investigate the as-fabricated sensor, changes in electrical resistance of sensors were examined under UV radiation with wavelengths of 365 and 390 nm with different intensities at low temperatures (<100 °C). The results indicate that it was improved by reducing in crystallite sizes of ZnO. A sensor with a crystallite size of about 20 nm showed the best response toward target gases. It could be because the particle size of the materials synthesized was comparable to the Debye length. Our study pointed out that the UV-activated sensor baxsed on MOS nanostructures was of good sensitivity, stability, and short response/recovery time at low temperatures, especially toward CO2 gas. The stability of CO2 due to the linear bonded atom makes it difficult to react with the target gas on the sensor. Therefore, considering the structural properties of CO2, sensor responses achieved in this work to different concentrations of CO2 are significant. Also, the Results obtained exhibit that optimal sensor response takes place at different intensities depending on the gas type. The selectivity of sensors could be tuned by UV light. In addition to examining gassensing properties, an unusual p-n transition was identified under UV light during gas-sensing measurements of sensor Z2, which has been thoroughly discussed in this work. The measurements for both gases showed that the pure ZnO sensors acted as a p-type semiconductor at room temperature. In contrast, they acted as an n-type semiconductor by increasing temperature.