What type of valves are included in the protection devices as per NFPA 54?

Check valves are an essential component in the protection devices outlined by NFPA 54. These valves allow the flow of gas in one direction while preventing backflow, which is crucial for maintaining safety and system integrity in gas distribution. If there were to be a reversal of flow, check valves act as a safeguard, preventing potentially dangerous conditions such as leaks or gas accumulation that could lead to hazardous situations.

In contrast, two-way and three-way valves primarily control the direction and flow of gas rather than providing a safety function against backflow. Control valves regulate pressure and flow but do not inherently provide the backflow prevention feature, which is specifically why check valves are emphasized in NFPA 54 guidelines as vital safety devices in gas systems.