CO2 exposure is a serious health risk for people if the concentration of CO2 is over the acceptable threshold. The severity of the risk depends on the concentration of CO2 and the length of the exposure. In an automobile, where the interior cabin is a closed volume (with minimal venting), the increase in concentration is detrimental to the customer but hard to detect. For applications where CO2 is used as the refrigerant for the air-conditioning system, the risk of CO2 exposure is increased due to the possibility of CO2 leakage into the cabin through the duct system. The initiation of the leak could be due to a crash event or a malfunction of the refrigerant system. In this paper, CFD is used to simulate the concentration of CO2 in the event of a leak. The methodology along with the advantages and limitations will be discussed. The simulations are being carried out in a C-segment car with five occupants in panel recirculation mode, as shown in the picture below. The assumption is that there is a refrigerant leakage of 50g/s for 8 seconds, and that each of the passengers are generating CO2 at 20 liters/hr. A transient simulation showing the increase in concentration of CO2 in the cabin is being conducted. Vehicle level testing and measurements are also planned and will be compared with the CFD results.