An over-pressure relief valve for use with a container housing a pressurized medium. The valve includes a hollow housing within which there is first and second valves. The first valve is operable to inject and release the pressurized medium into the container. The said valve is normally closed and is continuously exposed to the pressurized medium and in response to the pressure thereof reaching a predetermined level opens to exhaust the pressurized medium to the atmosphere to relieve the excess pressure.
