What device can be used to safely interrupt air flow in a pneumatic circuit?

A shut-off valve is designed specifically to stop or control the flow of air within a pneumatic circuit. Its primary function is to isolate different sections of a pneumatic system, which can be crucial for maintenance, safety, and troubleshooting. By closing the shut-off valve, the flow of compressed air is halted, preventing any air from escaping or being used downstream. This feature is particularly important in situations where you need to safely perform maintenance or repairs without the risk of air pressure causing accidents or injuries.

In contrast, other devices mentioned, such as pressure gauges, check valves, and trap valves, serve different purposes. Pressure gauges provide readings of the system's pressure but do not control flow. Check valves are designed to allow flow in one direction only and prevent backflow but are not meant for safely interrupting flow. Trap valves, used for removing condensate, do not serve the primary role of isolating the system. Hence, the shut-off valve is the most suitable device for safely interrupting air flow in the context of a pneumatic circuit.