Which practice is correct when pressure testing a fuel gas piping system?

Giải thích

The test medium must be air, nitrogen, carbon dioxide or another inert gas, and any equipment or regulator that cannot withstand the test pressure must be disconnected or isolated with a valve. Oxygen is prohibited because it reacts violently with pipe oils, appliance regulators are damaged by test pressures well above their rating, and locating leaks with a flame is never acceptable.