What is a field blank and why is it used?

• A. A field blank is a surface wipe collected from a known lead-free surface to validate results
• B. A field blank is a wipe or sampler opened in the field without surface contact, used to detect contamination introduced during sampling/handling
• C. A field blank is a sample collected after abatement to confirm remediation
• D. A field blank is a vacuum sample used to clean equipment

Answer: (B)

A field blank is a negative control used in sampling to detect contamination that can be introduced during collection or handling. It is a wipe or sampler opened in the field but without making contact with any surface, so any contaminants detected come from the sampling process itself rather than from the surface being tested. This helps verify that the collection method and handling procedures aren’t adding contaminants, ensuring that lab results truly reflect what’s on the test surfaces. If the field blank shows contamination, it signals that cross-contamination occurred during sampling or handling and that the sample results may need to be reviewed or treated with caution. It’s not a surface sample, nor a post-remediation check or a cleaning step.