Gas sensors based on metal oxide semiconductors (MOS) have been widely used for the detection and monitoring of flammable and toxic gases. In this paper, p-type Cr₂O₃ and Ti-doped Cr₂O₃ (CTO) thin films were synthesized using an aerosol-assisted chemical vapor deposition (AACVD) method. Detailed analysis of the thin films deposited, including structural information, their elemental composition, oxidation state, and morphology, was investigated using XRD, Raman analysis, SEM, and XPS. All the gas sensors based on pristine Cr₂O₃ and CTO exhibited a reversible response and good sensitivity to isobutylene (C₄H₈) and ammonia (NH₃) gases. Doping Ti into the Cr₂O₃ lattice improves the response of the CTO-based sensors to C₄H₈ and NH₃. We describe a novel mechanism for the gas sensitivity of p-type metal oxides based on variations in the oxygen vacancy concentration.