Is radon high in Sonoma County, California?

Low. The model predicts a long-term basement average of 1.4 pCi/L in Sonoma County (about 22% below the US average of 1.8 and close to the California average of 1.5). That is below the EPA's 2 pCi/L "consider fixing" threshold, though individual homes still vary. Ranked 49 of 58 California counties.

Should I test for radon in Sonoma County?

Yes, once. The EPA recommends testing every home regardless of area, and the model's ZIP-level predictions in Sonoma County already range from 1.3 to 1.8 pCi/L. A short-term kit costs little and settles the question for your house.

What does EPA Radon Zone 3 mean for Sonoma County?

Zone 3 - low potential (< 2 pCi/L). The zone map dates from 1993 and classifies whole counties. The 2001-2021 model agrees with the zone here. Neither replaces a test of your own home.

How much does radon mitigation cost in Sonoma County?

A standard active sub-slab depressurization system typically runs $800-$2,500 installed nationally; California quotes vary with foundation type (slab, crawlspace, basement), home size and local labor. Get two or three bids from certified mitigators listed by your state radon program or the EPA's find-a-professional page.

Radon levels in Sonoma County, California

LowEPA Zone 3

Predicted long-term basement average of 1.4 pCi/L (model estimate) across 32 ZIP codes - about 22% below the US average of 1.8, close to the California average of 1.5. Ranked #49 of 58 California counties.

Test Sonoma County, CA once anyway - radon varies house to house

The predicted basement average here is 1.4 pCi/L, below the EPA's 2 pCi/L "consider fixing" threshold. That's good news for the area - but the EPA still recommends every home be tested, because foundation cracks, soil pockets and ventilation make one house very different from its neighbor. One inexpensive kit settles it.

Get a short-term test kit →Or track it with a continuous monitor

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Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.

1.4 ± 0.06

pCi/L predicted basement mean (model SD)

0.7 ± 0.08

pCi/L predicted upstairs (above-ground) mean

1.3-1.8

range of ZIP-level basement predictions in the county

What this means for Sonoma

The typical Sonoma County home is predicted below 2 pCi/L, the lowest band. That is the best case an area can show - but it describes the average house, and the ZIP-level predictions within the county still span 1.3 to 1.8 pCi/L.

The 1993 EPA zone (3) and the 2001-2021 model agree for Sonoma. County figures weight each ZIP by its 2010 Census population, so they describe where people live rather than empty land.

Comparable California counties: Alameda County (1.4), Fresno County (1.4), Humboldt County (1.4), San Mateo County (1.4). The state's highest is Mono County at 2.7 pCi/L.

ZIP codes in Sonoma County

Predicted basement and upstairs means by ZIP (model estimate). ZIPs whose land is mostly in this county.

ZIP	Basement	Upstairs	Grade
95403	1.4 ± 0.06	0.7	Low
94928	1.4 ± 0.06	0.6	Low
95404	1.4 ± 0.06	0.7	Low
95407	1.3 ± 0.07	0.6	Low
94954	1.4 ± 0.07	0.7	Low
95401	1.3 ± 0.06	0.6	Low
95476	1.4 ± 0.07	0.8	Low
95492	1.5 ± 0.06	0.9	Low
95472	1.5 ± 0.07	0.7	Low
95409	1.5 ± 0.06	0.7	Low
95405	1.4 ± 0.06	0.7	Low
95448	1.5 ± 0.06	0.7	Low
95425	1.4 ± 0.06	0.8	Low
94931	1.4 ± 0.06	0.7	Low
94515	1.6 ± 0.06	1.0	Low
95436	1.6 ± 0.07	0.7	Low
95446	1.6 ± 0.08	0.7	Low
94951	1.4 ± 0.06	0.7	Low
95442	1.5 ± 0.06	0.8	Low
95465	1.7 ± 0.07	0.8	Low
95441	1.5 ± 0.06	0.8	Low
95421	1.8 ± 0.08	0.8	Low
95462	1.7 ± 0.07	0.7	Low
94923	1.5 ± 0.07	0.7	Low
95452	1.6 ± 0.06	0.7	Low
95497	1.4 ± 0.06	0.7	Low
95444	1.4 ± 0.07	0.8	Low
95439	1.4 ± 0.06	0.7	Low
94922	1.3 ± 0.08	0.7	Low
95412	1.4 ± 0.08	0.9	Low
95450	1.3 ± 0.07	0.6	Low
94972	1.3 ± 0.08	0.8	Low

If your test comes back at 4 pCi/L or higher

Mitigation is a routine job: a fan-driven pipe that vents soil gas from under the slab to above the roofline, typically $800-$2,500 installed (typical range; local quotes vary). Use certified professionals: EPA find-a-professional. Read the full mitigation guide.

Sonoma County radon questions

Is radon high in Sonoma County, California?: Low. The model predicts a long-term basement average of 1.4 pCi/L in Sonoma County (about 22% below the US average of 1.8 and close to the California average of 1.5). That is below the EPA's 2 pCi/L "consider fixing" threshold, though individual homes still vary. Ranked 49 of 58 California counties.
Should I test for radon in Sonoma County?: Yes, once. The EPA recommends testing every home regardless of area, and the model's ZIP-level predictions in Sonoma County already range from 1.3 to 1.8 pCi/L. A short-term kit costs little and settles the question for your house.
What does EPA Radon Zone 3 mean for Sonoma County?: Zone 3 - low potential (< 2 pCi/L). The zone map dates from 1993 and classifies whole counties. The 2001-2021 model agrees with the zone here. Neither replaces a test of your own home.
How much does radon mitigation cost in Sonoma County?: A standard active sub-slab depressurization system typically runs $800-$2,500 installed nationally; California quotes vary with foundation type (slab, crawlspace, basement), home size and local labor. Get two or three bids from certified mitigators listed by your state radon program or the EPA's find-a-professional page.

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