Radon levels in Chico, California
LowEPA Zone 3Predicted long-term basement average of 1.5 pCi/L (model estimate) across the 3 modeled ZIP codes in Chico - about 18% below the US average of 1.8, close to the California average of 1.5. Ranked #100 of 207 California cities on this site. Most of the city lies in Butte County.
Test Chico, 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.
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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
1.4-1.5
range of ZIP-level basement predictions in the city
0%
of Chico ZIPs predicted ≥ 4 pCi/L (0% ≥ 2)
What this means for Chico
The typical Chico home is predicted below 2 pCi/L, the lowest band. That describes the average house; the ZIP-level predictions inside the city still span 1.4 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). The 1993 EPA zone (3) for Butte and the 2001-2021 model agree here.
Comparable California cities: Fremont (1.5), Hayward (1.5), Orange (1.5), Palo Alto (1.5).
ZIP codes in Chico
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 |
|---|---|---|---|---|
| 95973 | 40% | 1.5 ± 0.06 | 0.7 | Low |
| 95928 | 39% | 1.5 ± 0.06 | 0.8 | Low |
| 95926 | 21% | 1.4 ± 0.06 | 0.8 | Low |
| 95929 | <1% | — | — | no model |
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.
Chico radon questions
- Is radon high in Chico, California?
- Low. Averaging the model's ZIP-code predictions across Chico (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. Chico ranks 100 of 207 California cities on this site.
- Which Chico ZIP codes have the highest radon?
- Predictions for the 3 modeled ZIP codes in Chico range from 1.4 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 Chico?
- Yes, once. The EPA recommends testing every home regardless of area. A short-term kit costs little and settles the question for your house; Chico's low predicted average describes the typical home, not yours.
- What does EPA Radon Zone 3 mean for Chico?
- Chico sits mainly in Butte County, which the EPA classifies as Zone 3 - low potential (< 2 pCi/L). The zone map dates from 1993 and covers whole counties. The 2001-2021 model agrees with the zone for the city. Neither replaces a test of your own home.
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