Is radon high in Fremont, California?

Low. Averaging the model's ZIP-code predictions across Fremont (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 1.5 pCi/L - about 18% 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. Fremont ranks 97 of 207 California cities on this site.

Which Fremont ZIP codes have the highest radon?

Predictions for the 5 modeled ZIP codes in Fremont range from 1.5 to 1.5 pCi/L in the basement. 0% of them are predicted at or above 4 pCi/L and 0% at or above 2. The city is fairly uniform, so the city-wide number is a reasonable guide for any neighborhood.

Should I test for radon in Fremont?

Yes, once. The EPA recommends testing every home regardless of area. A short-term kit costs little and settles the question for your house; Fremont's low predicted average describes the typical home, not yours.

What does EPA Radon Zone 2 mean for Fremont?

Fremont sits mainly in Alameda County, which the EPA classifies as Zone 2 - moderate potential (2-4 pCi/L). The zone map dates from 1993 and covers whole counties. The newer model's city average of 1.5 pCi/L does not line up with Zone 2, which is common - the EPA itself says high-radon homes exist in every zone. Neither replaces a test of your own home.

Radon levels in Fremont, California

LowEPA Zone 2

Predicted long-term basement average of 1.5 pCi/L (model estimate) across the 5 modeled ZIP codes in Fremont - about 18% below the US average of 1.8, close to the California average of 1.5. Ranked #97 of 207 California cities on this site. Most of the city lies in Alameda County.

Test Fremont, CA once anyway - radon varies house to house

The predicted basement average here is 1.5 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.

1.5 ± 0.06

pCi/L predicted basement mean (model SD)

0.8 ± 0.07

pCi/L predicted upstairs (above-ground) mean

1.5-1.5

range of ZIP-level basement predictions in the city

of Fremont ZIPs predicted ≥ 4 pCi/L (0% ≥ 2)

What this means for Fremont

The typical Fremont home is predicted below 2 pCi/L, the lowest band. That describes the average house; the ZIP-level predictions inside the city still span 1.5 to 1.5 pCi/L.

The city figure is not a separate estimate: it is the mean of the model's ZIP-code predictions, weighted by the share of the city's land in each ZIP (Census 2020 ZCTA-to-place relationship file). Note that the EPA classifies Alameda County as Zone 2 while the newer model predicts 1.5 pCi/L for Fremont; where they disagree, we grade on the model but show both.

Comparable California cities: Hayward (1.5), Orange (1.5), Chico (1.5), Palo Alto (1.5).

ZIP codes in Fremont

ZIPs that overlap the city, largest share of its land first. Predicted basement and upstairs means are model estimates; ZIPs the model does not cover show a dash.

ZIP	Share of city	Basement	Upstairs	Grade
94539	31%	1.5 ± 0.06	0.8	Low
94538	22%	1.5 ± 0.07	0.9	Low
94536	19%	1.5 ± 0.07	0.8	Low
94555	19%	1.5 ± 0.06	0.7	Low
94560	8%	1.5 ± 0.06	0.7	Low

Testing help in California

California's radon program page is at www.cdph.ca.gov; it lists testing and certified-mitigator guidance. EPA state radon contacts page. If a test comes back at 4 pCi/L or higher, mitigation typically costs $800-$2,500 installed; use EPA find-a-professional and read the mitigation guide.

Fremont radon questions

Is radon high in Fremont, California?: Low. Averaging the model's ZIP-code predictions across Fremont (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 1.5 pCi/L - about 18% 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. Fremont ranks 97 of 207 California cities on this site.
Which Fremont ZIP codes have the highest radon?: Predictions for the 5 modeled ZIP codes in Fremont range from 1.5 to 1.5 pCi/L in the basement. 0% of them are predicted at or above 4 pCi/L and 0% at or above 2. The city is fairly uniform, so the city-wide number is a reasonable guide for any neighborhood.
Should I test for radon in Fremont?: Yes, once. The EPA recommends testing every home regardless of area. A short-term kit costs little and settles the question for your house; Fremont's low predicted average describes the typical home, not yours.
What does EPA Radon Zone 2 mean for Fremont?: Fremont sits mainly in Alameda County, which the EPA classifies as Zone 2 - moderate potential (2-4 pCi/L). The zone map dates from 1993 and covers whole counties. The newer model's city average of 1.5 pCi/L does not line up with Zone 2, which is common - the EPA itself says high-radon homes exist in every zone. Neither replaces a test of your own home.

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