During brazing operations, purge gas is commonly used to prevent ignition. Which gas is typically used?

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

Answer: (A)

In brazing, purging the joint area with a gas creates an inert, oxygen-poor environment that prevents oxidation and reduces the chance of ignition from any flammable vapors. Nitrogen is the typical purge gas because it is non-reactive with most brazing alloys and metals at brazing temperatures, while also being inexpensive and readily available. This makes it effective at displacing air without introducing cost or reactive chemistry.

Argon and helium are also inert, but they are generally more costly and less practical for routine shop brazing. Oxygen would not be suitable, since it promotes oxidation and can support ignition, defeating the purpose of purging.