ASHRAE 34 defined a new class of refrigerants in 2010, namely Class 2L. It is expected that ASHRAE 15 will adopt new rules for the safe application of Class 2L refrigerants. Lacking technical justification for changes to the standard, work was undertaken to understand the behavior of Class 2L refrigerant under various leak scenarios. Air conditioning systems that directly serve the occupied space, or are located in the occupied space can leak refrigerant and, under the right conditions, be ignited. A series of CFD models were constructed that represent a room that could be served by such systems. Solutions were obtained with a variety of ventilation schemes. Leak rates were varied to examine the sensitivity of the solutions. In the end, results were obtained that demonstrate that safe application of Class 2L refrigerants is possible by placing certain restrictions on the equipment, potential ignition sources, and the ventilation system within the occupied space.