What system is fitted to oxygen regulators to prevent their use on inappropriate cylinder valves?

The pin indexing system is designed specifically to ensure that oxygen regulators can only be attached to compatible cylinder valves. This system uses a specific arrangement of pins that corresponds to the configuration of the outlet on the oxygen cylinder. Each type of gas has a unique set of pins, which prevents the accidental connection of an oxygen regulator to a cylinder containing a different gas, such as air or a different type of gas that might be incompatible with oxygen.

This is crucial because using an oxygen regulator on the wrong type of gas can lead to dangerous situations, including fire hazards or equipment failure. The pin indexing system is a critical safety feature in diving and other applications involving compressed gases, ensuring that proper procedures and safety protocols are maintained.

In contrast, a pressure relief valve serves to release excess pressure in the system but does not prevent misuse of regulators on incompatible cylinders. A safety blow-off cap is designed to manage potential pressure build-up but also does not address the compatibility of regulators and cylinders. Lastly, a flow restrictor controls the rate of gas flow in a system but does not influence the ability to connect different gas types and their associated regulators.