While an understanding of the dispersion of refrigerant in occupied spaces is important to ensuring the safety of occupants for spaces in which HVAC&R systems are installed, greatly simplified models are generally used to describe the complex refrigerant leakage phenomena. This paper describes some studies of transient behavior of refrigerant dispersion due to variations in the leakage rate, the exhaust ventilation rate, and the height of a wall undercut that could be used to develop improved models of the dynamics of refrigerant leaks. The results from these studies indicate that well-mixed models do not accurately describe the refrigerant distribution in many cases because of stratification, and that this stratification may be used in tandem with vent placement to ensure that refrigerant concentration levels do not exceed safety limits.