During brazing operations, purge gas used to prevent ignition is typically which gas?

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

Answer: (A)

During brazing, purging the joint area with a shielding gas helps keep air from causing oxidation and from igniting flammable vapors from flux or solvents. The gas chosen should be inert, affordable, and readily available. Nitrogen fits this role well: it is nonreactive under brazing conditions, it effectively displaces oxygen, and it won’t contaminate the joint or flux. Argon is also inert but more costly, so it’s used less often for routine brazing. Oxygen, on the other hand, would promote oxidation and increase the risk of ignition, which defeats the purpose of purging. Helium is inert too, but its higher cost and different practical handling make it less common for typical brazing operations. So the purge gas used to prevent ignition in brazing is nitrogen.