What common feature is found on regulators used with fuel gas cylinders?

The common feature of having left-hand threads on regulators used with fuel gas cylinders is significant since it helps prevent the accidental attachment of the wrong regulator to a cylinder. This ensures that only regulators designed for specific types of gases are connected, minimizing the risk of leaks or dangerous mixtures. Left-hand threads are specifically utilized on certain types of fuel gas cylinders as a safety measure, distinguishing them from other gas types that may use right-hand threads. This design feature is critical for maintaining safety standards in handling and using gas cylinders in various applications, including those used in welding, heating, and cooking.