Is radon high in Marin County, California?

Low. The model predicts a long-term basement average of 1.4 pCi/L in Marin County (about 23% 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 51 of 58 California counties.

Should I test for radon in Marin County?

Yes, once. The EPA recommends testing every home regardless of area, and the model's ZIP-level predictions in Marin County already range from 1.2 to 1.6 pCi/L. A short-term kit costs little and settles the question for your house.

What does EPA Radon Zone 3 mean for Marin 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 Marin 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 Marin County, California

LowEPA Zone 3

Predicted long-term basement average of 1.4 pCi/L (model estimate) across 27 ZIP codes - about 23% below the US average of 1.8, close to the California average of 1.5. Ranked #51 of 58 California counties.

Test Marin 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 ± 0.07

pCi/L predicted basement mean (model SD)

0.7 ± 0.07

pCi/L predicted upstairs (above-ground) mean

1.2-1.6

range of ZIP-level basement predictions in the county

What this means for Marin

The typical Marin 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 1.2 to 1.6 pCi/L.

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

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

ZIP codes in Marin County

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

ZIP	Basement	Upstairs	Grade
94901	1.3 ± 0.07	0.6	Low
94952	1.5 ± 0.07	0.7	Low
94941	1.5 ± 0.06	0.7	Low
94903	1.4 ± 0.07	0.6	Low
94947	1.4 ± 0.06	0.7	Low
94949	1.4 ± 0.06	0.7	Low
94945	1.5 ± 0.07	0.7	Low
94960	1.4 ± 0.06	0.6	Low
94920	1.4 ± 0.06	0.7	Low
94904	1.4 ± 0.06	0.7	Low
94965	1.2 ± 0.06	0.7	Low
94925	1.4 ± 0.07	0.7	Low
94930	1.4 ± 0.07	0.7	Low
94939	1.4 ± 0.07	0.7	Low
94964	1.2 ± 0.06	0.6	Low
94956	1.4 ± 0.07	0.7	Low
94924	1.4 ± 0.07	0.8	Low
94973	1.6 ± 0.07	0.8	Low
94933	1.4 ± 0.07	0.7	Low
94937	1.6 ± 0.07	0.9	Low
94938	1.4 ± 0.06	0.8	Low
94946	1.5 ± 0.07	0.8	Low
94970	1.4 ± 0.06	0.7	Low
94963	1.4 ± 0.06	0.7	Low
94971	1.2 ± 0.07	0.7	Low
94940	1.3 ± 0.07	0.7	Low
94929	1.4 ± 0.07	0.7	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.

Marin County radon questions

Is radon high in Marin County, California?: Low. The model predicts a long-term basement average of 1.4 pCi/L in Marin County (about 23% 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 51 of 58 California counties.
Should I test for radon in Marin County?: Yes, once. The EPA recommends testing every home regardless of area, and the model's ZIP-level predictions in Marin County already range from 1.2 to 1.6 pCi/L. A short-term kit costs little and settles the question for your house.
What does EPA Radon Zone 3 mean for Marin 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 Marin 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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