Which safety device is crucial in a gas piping system to prevent backflow?

The check valve is a vital safety device in a gas piping system specifically designed to prevent backflow. When gas flows in the desired direction, the check valve opens, allowing the gas to pass through. However, if there is a reversal in flow or pressure conditions that could lead to backflow, the valve closes, effectively stopping the gas from flowing backward into the system. This function is critical for maintaining system integrity, protecting equipment, and ensuring safety by preventing potential gas leaks or contamination.

In a gas piping system, each of the other devices has its own important role, but none serve the specific purpose of preventing backflow as effectively as the check valve does. Pressure relief valves are used to release excess pressure, shut-off valves are designed to stop gas flow during maintenance or emergencies, and regulators maintain proper pressure levels within the system. While all these components are essential for overall system safety and functionality, the unique operation of the check valve directly addresses the prevention of backflow, which is why it is the correct answer in this context.