Mold inspection and testing, and when you actually need it

Inspection vs. testing

Inspection

A visual and moisture-focused survey: moisture meters, sometimes thermal imaging, checking under sinks, behind access panels, in the attic and crawl space. The goal is to find where water is getting in and how far growth has spread.

Air sampling

Samples indoor air and compares it with an outdoor sample. Useful when there's a musty smell but no visible source, or to compare rooms.

Surface sampling

Tape or swab samples from a surface, analyzed by a lab. Useful to identify growth on a specific material or confirm a surface was cleaned.

Clearance testing

Done after remediation, before rebuild, to document that the work area is clean. Ideally performed by someone independent of the remediation company.

When testing is worth paying for

• A musty smell with no visible mold, which can point to growth inside walls, under flooring, or in ductwork.
• After a leak or flood, to see whether hidden materials stayed wet long enough to grow mold.
• Buying, selling, or renting, when you want documentation.
• After remediation, to confirm the job before walls are closed up.

When it usually isn't

The EPA says that in most cases, if visible mold growth is present, sampling is unnecessary, and since no federal limits exist for mold or spores, sampling can't be used to check compliance with a federal standard. If you can see it, the next step is usually finding the water and planning removal.

The EPA also notes that sampling should be done by professionals experienced in designing sampling protocols and interpreting results, with lab analysis following methods recommended by groups such as AIHA or ACGIH.