Start with the bottom line
CDPH says there are no recommended "unhealthy levels" for spore concentrations or particular kinds of mold, and that measuring mold doesn't tell you if there's a health problem (CDPH). If you can see or smell mold or moisture, you already know enough to act.
Common claims, and what CDPH says
- "Your indoor levels are higher than outdoors, so you have mold growth." CDPH says this comparison hasn't been scientifically proven, and mold levels vary widely over time both indoors and out.
- "You have toxic black mold." CDPH says there's no evidence the particular kind of mold matters; any mold you see or smell should be fixed.
- "We need a clearance test to prove it's gone." CDPH says no mold tests can currently show when remediation has succeeded. The best indicators are that the moisture source is fixed, damaged materials are removed or cleaned, and remaining materials are dry, with no visible mold or odor.
When results can still help
CDPH notes that testing may sometimes reveal hidden moisture that isn't obvious. Results can also be part of a real estate disclosure, an insurance file or a contract requirement. Ask whoever ran the test to explain what the results mean for decisions, and treat health conclusions cautiously.
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Buying or selling a home in Sonoma County
For buyers, a moisture-focused inspection of the crawlspace, attic, bathrooms and around windows usually tells you more than a spore count. Ask sellers about past leaks, floods and repairs. For homes near the Russian River, the Laguna or the Petaluma River, look up flood history and check FEMA's Flood Map Service Center.
Next steps
If your results came with a big remediation quote, a second opinion focused on moisture sources is reasonable. Request an inspection or read mold remediation basics.
Sources
Sources checked October 18, 2026.
Frequently asked questions
Should I retest after remediation?
CDPH says no test can show remediation succeeded. Look for a fixed moisture source, dry materials and no visible mold or odor.
Does a mold test help my insurance claim?
Insurers focus mostly on the cause of the water damage. Photos, dates and repair records usually matter more. Ask your insurer what they need.