This paper deals with the effect of Ag⁷⁺ ions on CO₂ gas sensing behavior of ZnO thick films. Zinc oxide thick film gas sensors are deposited on glass substrates using sol gel spin coating technique. The fabricated sensors are irradiated with 100 MeV Ag⁷⁺ ions at a fixed fluence of 3 x 10¹¹ ions/cm². The X-ray diffraction analysis of the samples before and after ion bombardment is carried out for structural characterization. The structural analysis has revealed that films exist in hexagonal wurtzite structure. The average crystallite size lies in nano-range. The gas sensing response to carbon dioxide before and after irradiation is carried. Investigation shows that there is change in operating temperature and sensitivity factor after irradiation.