North Bay Mold Remediation connects Marin and Sonoma property owners with local mold inspection and testing firms, and with remediation contractors when testing finds a problem.
When testing helps, and when it doesn't
The EPA's position is that in most cases, if mold growth is visible, sampling is unnecessary. You already know there is a problem, and the fix is the same whatever the species: correct the moisture and remove the growth. Air or surface testing earns its cost when:
- You smell mold but can't find it. See musty smell and hidden mold.
- You are buying or selling and want documentation. See home sale mold inspection.
- A landlord and tenant disagree about whether a problem exists
- Remediation is finished and you want to confirm the area is clean before walls close or people move back in. See clearance testing.
Three kinds of samples
Air samples
A pump draws a measured volume of air through a cassette for a few minutes, and a lab counts and identifies the spores collected. Air samples can point to a hidden source when indoor counts are noticeably higher than outdoors, or when types of mold show up indoors that aren't in the outdoor sample. Their limits are real. A sample covers only the few minutes it ran, spore levels swing with weather and activity, and mold sealed inside a wall may not release much into room air.
Surface samples
Tape lifts and swabs taken from a stain or surface tell you whether it is mold growth and what kind. The EPA notes that surface sampling may be useful to determine whether an area has been adequately cleaned or remediated, which is why it is often part of clearance testing.
ERMI and other dust tests
ERMI tests analyze settled dust for the DNA of a list of mold species and produce a single index score. They are widely marketed, but the EPA says ERMI is a research tool that has not been validated for non-research use, and it does not recommend routine public use in homes. If someone proposes an ERMI test, ask what decision it will help you make.
Why the outdoor sample matters
Mold spores are always in outdoor air, so a number by itself means little. The EPA says no federal limits have been set for mold or mold spores, which leaves interpretation to comparison: indoor rooms against an outdoor sample taken the same day, and suspect rooms against unaffected ones. Outdoor levels in the North Bay change with season and weather. A good report explains the comparison in plain language and ties it back to what the inspector saw and measured, not just a lab table.
Choosing who does the testing
The EPA recommends that sampling be done by professionals with experience designing sampling protocols and interpreting results, and analyzed using methods from groups such as AIHA or ACGIH. California has no mold inspector license and does not bar the same company from testing and remediating. We recommend using an independent testing firm anyway, so the results come from someone not paid for the cleanup. One related California rule: under Business and Professions Code 7197, a home inspector or their company may not do paid repairs on a structure they inspected in the past 12 months.
We connect owners across Marin and Sonoma, from Novato, Sausalito, and Tiburon to Petaluma and Santa Rosa. Testing is most useful paired with a full mold inspection that includes moisture readings, since moisture is what decides where mold grows.
On health, the CDC says mold can affect some people, especially those with allergies, asthma, or weakened immune systems. A test result can't tell you whether mold is affecting your health; your doctor is the right person to ask.
Want air or surface testing? Call (415) 234-5586 or request an estimate and we'll connect you with a local mold testing firm.
Mold remediation in Marin & Sonoma
- Mold Remediation → Containment, removal, and cleanup of mold growth in homes and rentals, following the IICRC S520 approach, with the moisture source fixed first.
- Mold Removal & Black Mold Removal → Removing visible mold, including dark-colored growth people call black mold, from walls, ceilings, framing, and contents.
- Mold Inspection & Testing → Visual inspection, moisture mapping, and air or surface sampling to find hidden mold and its water source.
- Mold Clearance Testing → Independent post-remediation testing that confirms the job is done before walls close up or tenants move back in.
- Crawl Space Mold Remediation → Mold on joists, subfloor, and sill plates under raised-floor homes, plus the drainage and vapor fixes that keep it from returning.
- Attic Mold Remediation → Mold on roof sheathing and rafters from leaks, bath fans venting into the attic, and poor ventilation.
- Mold After Water Damage or Flooding → Drying, tear-out, and mold remediation after leaks, burst pipes, and Russian River and creek flooding.
- Bathroom Mold Removal → Mold in shower walls, behind tile, under floors, and on ceilings from leaks and bathrooms without working fans.
- Wall & Drywall Mold Removal → Cutting out and replacing moldy drywall and insulation, and finding the leak or condensation behind it.
- Musty Smell & Hidden Mold Investigation → Tracking down the source of a musty odor when no mold is visible, from wall cavities to crawl spaces and ducts.
- HVAC & Duct Mold → Mold in furnace cabinets, air handlers, and ductwork, coordinated with an HVAC contractor where equipment work is needed.
- Plumbing Leak & Under-Sink Mold → Mold from slow leaks under sinks, behind dishwashers and toilets, and around water heaters and washing machines.
- Rental Mold Inspection & Remediation → Mold in rentals for landlords and tenants: visible mold as a substandard condition under state law, code enforcement, and documentation.
- Home Sale Mold Inspection → Mold inspections during escrow, since termite reports exclude mold, plus remediation before listing or closing.
- Commercial Mold Remediation → Mold remediation for offices, retail, multi-unit buildings, and property managers, scheduled around tenants and operations.
- Mold Air Quality Testing → Air sampling and ERMI-style dust testing, what the lab report can and cannot tell you, and when testing is worth paying for.
Frequently asked questions
Is there a safe level of mold in indoor air?
There is no official one. The EPA says no EPA or other federal limits have been set for mold or mold spores, so a lab result cannot be checked against a federal standard. Results are usually interpreted by comparing indoor samples with outdoor samples taken at the same time, and by looking at which types of mold show up.
Should I buy a home mold test kit?
Settle plates and other do-it-yourself kits usually grow something, because mold spores are present nearly everywhere. Without an outdoor comparison and someone trained to interpret the result, they rarely answer the question you have. The EPA recommends that sampling be done by professionals with experience designing sampling protocols and interpreting results.
What is an ERMI test?
ERMI, the Environmental Relative Moldiness Index, analyzes settled dust for the DNA of a set list of mold species. It was developed by EPA researchers, but the EPA says it is a research tool and does not recommend routine public use of ERMI in homes, schools, or other buildings.
How much does mold air testing cost?
It depends on the number of samples and the lab. Published cost guides put a typical inspection with two to four samples at roughly $300 to $700, and clearance tests in a similar range. Ask how many samples are included and whether an outdoor sample is one of them.
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