Which item is essential to prevent loss of gas for cylinders in a central supply system if damage occurs?

The check valve is vital in a central supply system for medical gases because it ensures that gas can only flow in one direction. This prevention of backflow is crucial; in the event of a system failure or damage, a check valve will stop gas from escaping the system, which is essential in maintaining supply integrity and safety. Without a functioning check valve, gas could leak out of the system, leading to wasted resources and potential hazardous conditions.

The other components mentioned, while important for the overall functioning and safety of the gas supply system, do not serve the same purpose as a check valve in dealing specifically with the risk of loss of gas due to damage. For example, a regulator controls the pressure of the gas but does not prevent backflow, while a relief valve ensures safe pressure levels to avert overpressure situations, and a pressure gauge monitors the pressure but does not influence gas flow direction. Therefore, in the context of preventing gas loss if damage occurs, the check valve is indispensable.