This is a series of what is called “pop-type” relief valves. They are specifically created for use as secondary relief valves in carbon dioxide transports and stationary storage tanks. This type of valve is made to protect the tank from excessive pressure, in the event of fire or other emergency. A small throttling-type primary relief valve must also be provided to control boil-off and maintain tank pressure. Arrangements should be made to avoid any accumulation of water or foreign material within the valve. These relief valves will “pop” open to full capacity whenever pressure exceeds a certain point.