During brazing, which gas is commonly purged through the line into the compressor to prevent fire or explosion?

• A. Oxygen
• B. Argon
• C. Nitrogen
• D. Helium

Answer: (C)

During brazing, the goal is to remove air and any flammable vapors from the line so the hot torch doesn’t ignite them. Purging with an inert, non-flammable gas creates a safe, oxygen-poor environment inside the line. Nitrogen is used because it’s inert, cheap, and readily available, and it effectively displaces air and vapors, lowering the risk of fire or explosion when the joint is heated. Oxygen would support combustion, making a fire more likely, while argon is inert but typically more costly, and helium is not practical for this use.