To assure that all ambient air has been removed from the pipeline prior to brazing, a/an ______ shall be used to verify the effectiveness of the nitrogen purge.

• A. air analyzer
• B. nitrogen analyzer
• C. oxygen analyzer
• D. breathalyzer

Answer: (C)

During nitrogen purging, the goal is to replace ambient air with an inert environment by removing oxygen from the line. The best way to confirm that this purge is complete is to monitor the oxygen level inside the pipeline. An oxygen analyzer directly measures the concentration of O2, so once the reading falls to the required low level (as specified by the procedure), you know that residual air has been effectively displaced and it’s safe to braze.

Using a nitrogen analyzer wouldn’t tell you whether oxygen is present or absent, since it focuses on nitrogen content. An air analyzer isn’t specific to oxygen in a closed system, and a breathalyzer is unrelated to industrial piping.