Radon in Mendocino County, California
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Mendocino County is one of 27 California counties (out of 58) that EPA places in Zone 3. 29 ZIP codes reach into the county, 25 of them entirely.
What the zone means for a Mendocino County home
Zone 3 means EPA predicted a county-wide average below 2 pCi/L. Many Mendocino County homes will test low, but EPA has found homes above the action level in every Zone 3 county it studied, so a low zone is not a pass.
A short-term test kit costs little and takes two to seven days. If your result is 4 pCi/L or higher, EPA recommends a follow-up test and, if it is confirmed, a mitigation system, which typically uses a pipe and fan to pull soil gas from under the foundation and vent it above the roof. Check a result with the level calculator and plan your next step with the follow-up planner.
Finding a radon professional in Mendocino County
We have not added California professionals yet. Until we do, use the California radon program (CA Indoor Radon Program, 916-449-5674) at www.cdph.ca.gov/radon, or the national certification boards: the NRPP pro search and NRSB find a pro. Or ask for free quotes below.
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ZIP codes in Mendocino County
Open a ZIP to see every county it touches. Where a ZIP crosses a county line, the percentage is the share of its land area inside Mendocino County.
California radon program
EPA lists CA Indoor Radon Program (phone 916-449-5674) as the state contact. State programs can tell you about local test results, discounted kits, disclosure rules for home sales and credentialed professionals. Website: www.cdph.ca.gov/radon.
Back to all California counties.
Frequently asked questions
What is the EPA radon zone for Mendocino County, California?
EPA's Map of Radon Zones puts Mendocino County in Zone 3 (low potential): Predicted average indoor screening level below 2 pCi/L.
Do I need to test for radon in Mendocino County if the zone is low?
Yes. EPA says the zone map should not be used to decide whether a single home needs testing. Homes with high radon are found in every zone, and neighboring homes can test very differently. Testing is cheap and the only way to know your level.
How do I find a certified radon professional in Mendocino County?
Ask the California radon program (CA Indoor Radon Program, 916-449-5674) for its list of credentialed professionals, or search the national certification boards, NRPP and NRSB. You can also ask for free quotes with the form on this page.
How many ZIP codes are in Mendocino County?
29 ZIP codes have at least part of their land area in Mendocino County, based on the U.S. Census Bureau's 2020 ZIP Code Tabulation Area to county relationship file.
Free checklist · PDF
Radon Test Checklist
A one-page, step-by-step checklist for running a home radon test right the first time, and what to do with the number.
- Short-term vs. long-term test: which to use
- Closed-house conditions and where to place the kit
- What 2, 4 and 8 pCi/L mean and when to fix
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