The first operation is to ________ the ________ lines.

• A. Purge, sample
• B. Flush, air
• C. Test, lines
• D. Clean, lines

Answer: (A)

Purging the sample lines is the first essential step because it clears out any residual gas, moisture, or contaminants left in the line. By pushing clean gas through the line, you replace whatever was in there with a known baseline, so the analyzer reads accurately when you test or sample the current gas. This prevents carryover from previous samples or ambient air from skewing results. Flushing the air lines, testing the lines, or simply cleaning the lines don’t guarantee that old contents are removed or that the baseline is defined, so they’re not the correct first action in preparing for a measurement.