PdO films were obtained by thermal deposition of palladium metal with a thickness of 30 and 90 nm, followed by its oxidation in air at different temperatures. PdO oxide films are characterized by transmission electron microscopy (TEM) and reflection high-energy electron diffraction (RHEED). Data on the semiconductor properties and gas sensitivity to different concentrations of ozone in the air are obtained. The optimal temperature conditions for the oxidation of the films are established, which ensure their uniform phase composition and the absence of electrical noise during the detection of gases. The mechanism of the electrical noise appearance in ultrathin films associated with their fragmentation during oxidative annealing is proposed and justified. The possibility of detecting ozone impurities in the air below the maximum permissible concentration (MPC) by PdO semiconductor films is shown.