Abstract: A refrigerant charging system and method for charging a refrigeration system with a vapor-phase refrigerant includes a refrigerant source, an input line, a sensor and a pressure regulator. The input line connects the refrigerant source to the refrigeration system. One or more valves are disposed between the refrigerant source and refrigeration system to regulate the pressure of the refrigerant being introduced into the refrigeration system, and the sensor measures the pressure of the refrigerant entering the refrigeration system. A pressure regulator can also be used to regulator the flow of refrigerant. Once the pressure of the refrigerant reaches a predetermined pressure, the refrigeration system is fully charged, and the transfer of refrigerant to the refrigeration system is stopped. The system and method are used to charge the refrigeration system of, e.g., an automotive vehicle, and the refrigeration is carbon dioxide.