US Patent 7814757 Operating algorithm for refrigerant safety system

A method of operating a directed relief valve to ventilate a refrigerant by sensing the concentration of refrigerant leakage from the air conditioning system, and if the first concentration exceeds a threshold, by sensing a second concentration. If the first and second concentrations exceed a predetermined concentration, the system will send a leak message to the operator and/or ventilate the refrigerant to the surrounding atmosphere. The system continuously monitors the refrigerant leakage concentration when the vehicle engine is operative, but only periodically monitors the refrigerant leakage concentration when the vehicle engine is inoperative.