If upper and lower walls have different painting histories, how many tests are required for that wall pair?

If upper and lower walls have different painting histories, how many tests are required for that wall pair?

• A. Two tests are required for each wall.
• B. Four tests are required of each.
• C. One test is sufficient.
• D. Six tests are required for all walls.

Answer: (B)

When two walls have different painting histories, you must treat them as separate testing units because each wall may have lead in a different layer or coating. To be sure about both walls, you collect independent samples from each wall and replicate testing to confirm results. You typically take two tests on the upper wall and two on the lower wall, giving four tests for the wall pair. This two-per-wall approach helps verify results across the differing layers and reduces the chance of a false negative or false positive due to a single sample.

When two walls have different painting histories, you must treat them as separate testing units because each wall may have lead in a different layer or coating. To be sure about both walls, you collect independent samples from each wall and replicate testing to confirm results. You typically take two tests on the upper wall and two on the lower wall, giving four tests for the wall pair. This two-per-wall approach helps verify results across the differing layers and reduces the chance of a false negative or false positive due to a single sample.