How to read mold test results

A mold report can look precise—numbers, species names, spores per cubic meter—but interpretation is contextual. Start with what was sampled, why it was sampled, and what the building inspection found.

1. Confirm the sample type

Air, surface, tape-lift, swab, and bulk samples answer different questions. Do not compare unlike methods as though they are the same measurement.

2. Find the outdoor control

For indoor air sampling, the outdoor sample provides environmental context. Compare totals, but also compare the types and relative distribution of spores.

3. Look beyond the grand total

A total can hide a strong indoor signal from one group. Conversely, a high outdoor day can drive both outdoor and indoor totals upward without proving indoor amplification.

4. Connect the lab sheet to the building

Known leaks, wet materials, musty odor, visible growth, condensation, and humidity history can be more actionable than a single short-duration air sample.

5. Avoid fake precision

Sampling captures a moment in time. Airborne spores can vary with activity, HVAC operation, doors and windows, cleaning, weather, and where the sampler was placed.