A gas fired system operating at 2 PSI should be tested using which substance?

A gas fired system operating at 2 PSI should be tested using air because it allows for a non-hazardous method of pressure testing the system. Air testing helps to identify leaks by monitoring pressure drops over a specified period. Testing with air is particularly advantageous as it doesn't pose the risk of igniting or causing explosive mixtures since gas is present in the system, which would be the case if the system were tested with gas.

Using air for pressure testing also provides visual and audible cues in the form of sounds from escaping air if any leaks are present. This is crucial for ensuring safety and performance before the system is powered with gas. In comparison, other substances like water, oil, or gas would not provide the same level of safety and reliability in testing for potential leaks in a gas-fired system. Water could potentially cause corrosion, and testing with gas would be hazardous and impractical due to the risk of explosion.