What is the test medium for valves on gas service?

The test medium for valves on gas service is typically a non-combustible gas, such as nitrogen or air, depending on the specific testing requirements and regulations. These gases are used to pressurize the system and check for leaks without introducing any flammable materials. It's essential to conduct these tests in a controlled environment to ensure safety and compliance with industry standards. Always refer to relevant guidelines and standards for specific testing procedures.