When using XRF and sodium sulfide tests, what should never be concluded if results conflict?

When considering the use of X-ray fluorescence (XRF) and sodium sulfide tests in lead inspection, it's crucial to understand the significance of conflicting results. If there is a disagreement between the two test results, concluding that "lead is not present" is an incorrect inference.

This is because XRF testing provides a direct measurement of lead in paint or materials, while sodium sulfide tests reveal the presence of lead based on chemical reactions. If these tests provide contradictory results, it indicates uncertainty regarding the actual presence of lead, rather than confirming its absence.

Therefore, the appropriate course of action in the event of conflicting results is to consider the results inconclusive or to pursue further testing to clarify the situation. This cautious approach ensures that no assumptions are made regarding lead's presence or absence, which is a critical aspect of ensuring safety in environments where lead exposure could be a concern.