CO2 is an alternative to replace the conventional refrigerant (R134a) for the air-conditioning system, due to the high Global Warming Potential (GWP) of R134a. There are concerns with the use of CO2 as a refrigerant due to health risks associated with exposure to CO2, if the concentration of CO2 is over the acceptable threshold. For applications with CO2 as the refrigerant, the risk of CO2 exposure is increased due to the possibility of CO2 leakage into the cabin through the duct system; this CO2 is in addition to the CO2 generated from the respiration of the occupants. The initiation of the leak could be due to a crash event or a malfunction of the refrigerant system. In an automobile, where the interior cabin is a closed volume (with minimal venting), the increase in concentration can be detrimental to the customer but is hard to detect.In this paper, the concentration of CO2 in the event of a leak is studied - Computational Fluid Dynamics (CFD) is used to simulate the concentration of CO2 in the cabin and the results are validated with experimental measurements. A transient simulation showing the increase in concentration of CO2 in the cabin is conducted as a preliminary demonstration of the usefulness of the CFD tool in cabin CO2 dispersion - the CFD model is able to accurately capture the trends and values of the CO2 concentration in the cabin as a function of time.