How should calibration be conducted on a known lead surface?

Calibration on a known lead surface should ideally involve testing multiple times to ensure accuracy and reliability of results. By testing three times and averaging the results, you minimize the potential for outliers or errors in any single measurement that could skew the data. Averaging helps to provide a more accurate representation of the lead surface condition as it accounts for variability in testing conditions, operator technique, and instrument response.

This approach is particularly important in lead risk assessment because precise measurements are crucial for determining levels of exposure and compliance with safety standards. It provides a more robust dataset which can be critical for making informed decisions about lead hazards.

Single measurements can be misleading, as they don’t reflect potential fluctuations or variations that could occur in testing. A visual inspection alone wouldn't provide quantitative data on lead levels, and utilizing a different radioactive source would not be relevant to the calibration process on a known lead surface.