What this covers
Mold testing starts with an inspection: the tester looks for staining, odor and water damage and takes moisture readings in walls, floors and ceilings. Where sampling is useful, a qualified tester draws a measured volume of air through a cassette with a calibrated pump, indoors and outdoors for comparison, and may take tape or swab samples from suspect surfaces. The samples go to a lab, and the report lists the types of spores found and how indoor counts compare with the outdoor baseline. Testing helps scope remediation and confirm it afterward; finding the moisture source still matters most.
When to call
- A musty smell with no visible source.
- A past leak or flood where you are unsure whether growth started behind finishes.
- Remediation that is finished and needs clearance sampling.
- Staining you want identified before deciding on the next step.
What to expect
- InspectThe tester looks for water damage and takes moisture readings around the suspect area.
- SampleAir samples are drawn indoors and outdoors, and surface samples taken where they help.
- Lab analysisSamples are sent to a lab under chain of custody and analyzed for spore types and counts.
- ReportThe tester explains the lab results alongside what the inspection found.
Get a certified company
Look up a certified company by ZIP code. Every company's license, insurance and trades are verified before it is listed, and placement is never paid.
Questions people ask
Why is an outdoor sample taken?
Mold spores are always present outdoors. The outdoor sample is the baseline the indoor results are read against.
Is testing always needed?
Not always. Visible growth with a known water source can go straight to remediation planning; testing helps when the source or extent is unclear, and to confirm clearance afterward.
What does a lab report show?
The spore types identified in each sample and their counts, set beside the outdoor baseline, along with notes on the sampling conditions.
Related: Mold remediation · Home inspection · Whole-home dehumidifiers · All inspections and testing
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