Mold can grow in drain pans, on coils, and in ducts, especially ducts running through damp crawlspaces. The EPA advises not running a system you suspect is contaminated. Here's how that plays out in Sonoma, what to do right now, and how to reach an independent, licensed local provider. Call (628) 336-1777 any time, or use the form on this page.
HVAC and duct mold in Sonoma: what we see
Older Sonoma homes may have older ducts in crawlspaces or basements, where dampness leads to mold.
Older Sonoma homes may have older furnaces and ducts in crawlspaces or basements. Damp conditions there can affect ductwork.
The local picture
Heating systems in local homes. House age and type determine what heating systems and ducts are common. Sonoma has older and historic homes near the Plaza alongside newer neighborhoods.
Neighborhoods include the Plaza area, the east and west sides of town, and nearby valley communities. Conditions vary from street to street, so a provider should look at your specific home rather than assume.
What to do right now
- Turn off the system if you suspect mold in it.
- Note where the musty smell is strongest and when it happens.
- Check the filter and drain pan, if accessible.
- Don't spray chemicals into the ducts.
- Call an HVAC professional or mold provider for an inspection.
Want a local pro to take a look?It's free for homeowners and there's no obligation.
Sonoma checklist
- Inspect ducts in damp spaces.
- Change filters on schedule.
- Keep condensate lines clear.
- Seal and insulate ducts in crawlspaces.
- Control crawlspace humidity.
Local resources for Sonoma
- Permits: City of Sonoma (Permit Sonoma outside city limits)
- Emergency alerts: SoCoAlert, the County's free notifications
- Sandbags: Sonoma County sandbag locations, updated during weather events
- Contractor licenses: CSLB license check
How a provider handles it
An inspection finds where growth is and why. The fix may include cleaning components, replacing lined or damaged ducts, and correcting the moisture source. For the full picture, read our complete guide and the deep dive Mold testing: what California says. We also have a storm-season article: Mold in rental housing.
Before you hire anyone, check the license on the CSLB site. Here's how we vet providers.
Dealing with this right now?Tell us what's happening and we'll connect you with an independent local provider.
More for Sonoma
- Mold removal in Sonoma: our full local page
- HVAC and duct mold service
- Crawlspace mold in Sonoma
- Attic mold in Sonoma
- Bathroom mold in Sonoma
- Mold after flooding in Sonoma
- Same problem nearby: HVAC mold in Glen Ellen & Kenwood, HVAC mold in Petaluma, HVAC mold in Santa Rosa
- HVAC and duct mold in every Sonoma County town
Sources
Sources checked October 18, 2026.
Frequently asked questions
Is duct mold common in older homes?
It can be where ducts run through damp areas.
Is it worth replacing old ductwork?
If it's damaged or contaminated, often yes.
Will duct cleaning fix mold?
Cleaning addresses existing growth; moisture control prevents it. See EPA guidance.
Who should I call?
An HVAC contractor (check their CSLB license) or a mold remediation provider, depending on the scope.