Medical oxygen cylinders come with one of two types of valves: CGA-870 or CGA-540.

Each gas and its corresponding service are given a unique connector by the Compressed Gas Association (CGA) to help avoid any confusion with different types of compressed gases.

When it comes to Post Valve Connections, you will need a tool to open them up. These connections rely on a pin indexing system, where the valve has drilled holes that allow pins from specifically designed equipment to fit perfectly during connection. For oxygen services, the CGA-870 connection features two holes just below the valve opening, ensuring the equipment aligns correctly with the valve. If it does not fit, then the equipment is not meant for oxygen service. You will find the CGA 870 valve on smaller cylinders, such as M6, C, D and E.

Threaded Valve Connections usually have a spigot-type connection that you turn to open the valve. These are built with a unique threading system specific to different gas services. The size, direction and type of threading are tailored for each gas service. For a successful connection, the equipment must have threading that matches the valves. In the case of oxygen services, the CGA-540 valve has threads that turn clockwise on a male connection, requiring a matching clockwise thread on a female connection for a secure fit. Incorrect connections suggest the equipment is not suitable for oxygen service and should not be modified to fit.

Larger cylinders, such as H and T, typically come with the CGA 540 cylinders.