Drivers in hot and humid countries tend to operate the vehicle air conditioner system in the recirculation mode when driving. However, this causes the concentration of carbon dioxide (CO2) in the cabin to rise sharply, potentially resulting in dizziness, drowsiness and other traffic safety hazards. In the fresh air mode, suspended particles and contaminants are introduced into the cabin along with the outside air, posing further health risks to the occupants. Thus, it is important to evaluate the optimal ventilation strategy for vehicle cabins. Accordingly, the present study performs computational fluid dynamics (CFD) simulations to investigate the indoor air quality (IAQ) in the cabin of a compact passenger vehicle under various ventilation/circulation modes. The validity of the CFD model is confirmed by comparing the simulation results for the IAQ in the cabin with the experimental data reported in the literature. An air-conditioning ventilation strategy is proposed for maintaining the CO2 concentration in the cabin between 1000 ppm and 2000 ppm. The feasibility of the proposed strategy is investigated for various numbers of occupants in the cabin (1, 2, and 5 people) and air filters with different filtration efficiencies of 20%, 40%, and 80%, respectively. The results show that as the number of people in the cabin increases, the frequency at which switching between the two ventilation modes is required increases. Moreover, the relative proportion of time for which the fresh air mode is needed also increases. The concentration of suspended particles in the vehicle cabin increases as the duration of the fresh air mode increases. However, the particle concentration reduces significantly as the filtration efficiency of the air filter is increased.