What defines an acceptable field duplicate sample?

• A. A second wipe sample from a far away surface
• B. A second wipe sample from a similar surface area near the original surface to assess sampling precision.
• C. A second air sample from the same surface
• D. A single wipe sample from a different room

Answer: (B)

Field duplicates are used to check the precision of the surface sampling process. The idea is to repeat the same wipe method on a surface that is similar to the original area and is located nearby. This setup keeps the surface characteristics comparable while providing an independent sample, so you can see how consistent the collection technique and subsequent analysis are. If the duplicate yields a result similar to the original, it indicates good sampling precision; large differences point to variability in technique or small-scale surface heterogeneity.

Choosing a far away surface would introduce different surface conditions and dust loading, which confounds precision. Taking a second air sample or a single wipe from a different room doesn’t test the repeatability of the wipe sampling on a comparable surface, so it doesn’t serve as a proper field duplicate.