What we collect
A standard residential air sample is a 5-minute draw of room air across a spore-trap cassette. The cassette is sent to an accredited third-party lab where a microscopist counts and classifies the spores stuck to it.
You will see at least two cassettes in our scope: one indoor sample of the room in question, and one outdoor control taken just outside the building during the same 5-minute window. The outdoor sample is the baseline you compare the indoor numbers against.
What the report tells you
A typical lab report comes back with:
| Field | What it means |
|---|---|
| Total raw count | Number of spores actually seen on the cassette under the microscope |
| Spores per cubic meter (spores/m³) | Raw count adjusted for the volume of air sampled. This is the number that matters. |
| Species breakdown | Per-genus count: Cladosporium, Penicillium/Aspergillus, Alternaria, etc. |
| Water damage indicators | A short list of species that almost never appear without sustained moisture intrusion (Stachybotrys, Chaetomium, Memnoniella, Fusarium) |
| Hyphal fragments | Pieces of mold structure, not whole spores. Elevated counts suggest a colony was disturbed recently. |
| Background debris | Skin cells, fibers, dust. High debris can reduce spore-count accuracy. |
What the numbers actually mean
There is no published EPA or OSHA action level for indoor mold spore counts. Anyone who tells you otherwise is selling something. The interpretation is always comparative.
The rough rules of thumb we use after thousands of samples:
- Indoor count below outdoor count, similar species mix: nothing to act on.
- Indoor count 1.5x to 2x outdoor, similar species mix: monitor. Could be normal seasonal variation.
- Indoor count 2x to 4x outdoor, similar species mix: investigate. Likely a moisture source somewhere.
- Indoor count more than 4x outdoor, OR very different species mix from outdoor: usually warrants remediation.
- Water damage indicators (Stachybotrys, Chaetomium, etc.) at any count: investigate. These don't drift in from outdoors.
The trap to avoid
A common mistake homeowners make is comparing their report to numbers they've seen on someone else's report online. Spore counts vary enormously by region, season, day of the week, even hour of the day. A 'high' count in Seattle in February is a 'low' count in Idaho Falls in August. The only baseline that matters is the outdoor sample taken at the same time as your indoor one.
What a single sample can and can't tell you
Can tell you:
- Whether the air in this specific room at this specific moment is elevated
- Whether water-damage-indicator species are present
- Whether the species mix matches or differs from outdoor
Can't tell you:
- Where the source is (you need moisture mapping + thermal imaging + a visual walk for that)
- How long the elevation has been there
- Whether anyone is being made sick by it (that's a medical question)
- Whether a remediation has succeeded (that's what the post-remediation clearance sample is for)
Next step
If you have a report you want a second opinion on, or you're deciding whether to test at all, send a photo of the area and your situation at moldremovalandtesting.com/photo-check. For a paid inspection with full sampling, book at moldremovalandtesting.com/schedule. Single-room standard residential testing runs about $250 to $450.