What gas do we use to test NH3?

The correct answer is nitrogen (N2) because nitrogen is an inert gas that does not react with ammonia (NH3) during pressure testing. When conducting a pressure test on ammonia piping systems, nitrogen is preferred because it helps to avoid any chemical reactions that could lead to hazardous situations or equipment damage. Nitrogen's inert properties ensure that the integrity of the ammonia system is maintained without introducing additional variables that could compromise safety or reliability.

Utilizing nitrogen for testing also allows for better pressure control during the testing process, as it can be easily regulated and does not contribute to any pressure reactions like some other gases might. This makes nitrogen an ideal choice in high-pressure scenarios such as those often found in ammonia systems.