We focus on ozone (O3) detection at ambient temperature by Zinc Oxide (ZnO) nanoparticles (NPs) deposited on Si/SiO2 by spin coating from colloidal solutions as sensitive layers for air quality monitoring. We establish that at room temperature using continuous Ultra-Violet (UV) light irradiation enhances the sensing responses. Three annealing temperatures of ZnO films were performed to compare the sensing properties. These sensors present repeatable responses towards O3 with fast responses for concentrations as low as 35 ppb with processes compatible with most of flexible substrates.