Abstract: A refrigerant loss prevention system is disclosed that monitors a number of variables within a refrigerant circuit including both environmental and refrigerant conditions and arrives at expected refrigerant conditions utilizing the sensed environmental conditions. The sensed refrigerant conditions are compared to the expected refrigerant conditions, and alarms are actuated should the two differ by more than a preset amount. The refrigerant loss prevention system continues to operate when the refrigerant circuit is off to identify leaks even during long periods of down time, such as winter.