CHICAGO — Mold testing is a valuable tool for assessing indoor air quality and verifying the effectiveness of remediation work, but it must be performed correctly and interpreted in context to provide meaningful information — and it is not always necessary or appropriate.
The most common types of mold testing are air sampling, surface sampling (swab or tape lift), and bulk sampling (physical collection of a material sample). Air sampling measures the concentration of mold spores in the air and is the most useful test for assessing occupant exposure and verifying post-remediation conditions. Surface sampling identifies the species of mold present on a specific surface. Bulk sampling is used to determine whether a material is contaminated.
Air sampling should always include both indoor samples and outdoor reference samples taken at the same time. The comparison between indoor and outdoor spore counts is the key metric — indoor counts that are significantly higher than outdoor counts, or that contain species not found outdoors, indicate a potential indoor mold problem.
The IICRC S520 standard recommends that post-remediation verification testing be performed by an independent industrial hygienist who was not involved in the remediation work, to ensure objectivity. The standard also specifies that post-remediation samples be compared to samples from unaffected reference areas within the same building.
Homeowners should be cautious about do-it-yourself mold test kits, which are widely available but often provide misleading results. Passive settle plate tests, which collect spores that fall onto a petri dish, are not representative of actual airborne spore concentrations and cannot be used to assess occupant exposure or verify remediation effectiveness.
