How to Read a Mold Laboratory Report Without Guessing

Start with the outdoor column

Read the outdoor control first, then compare each indoor location against it. An indoor sample dominated by species that barely appear outdoors is a stronger indicator than a raw number by itself.

Genera worth noticing

Cladosporium and Alternaria are common outdoors and often normal indoors at similar levels. Aspergillus/Penicillium, Chaetomium and Stachybotrys indoors typically point to water-damaged materials, because those groups need sustained wetness on cellulose.

What the report cannot tell you

A laboratory report identifies and counts what was on the sample. It does not diagnose health effects, locate the leak, or set a legal threshold. There is no federal numeric limit for indoor mold, which is why the inspector's moisture findings and photographs are as important as the counts.

• Sample location and volume for each cassette
• Raw count versus counts per cubic meter
• Background debris rating, which can mask spores
• Chain of custody and accreditation details