Radon levels in San Jose, California
LowEPA Zone 2Predicted long-term basement average of 1.5 pCi/L (model estimate) across the 29 modeled ZIP codes in San Jose - about 19% below the US average of 1.8, close to the California average of 1.5. Ranked #104 of 207 California cities on this site. Most of the city lies in Santa Clara County.
Test San Jose, 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.
We may earn a commission from Amazon at no extra cost to you.
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 ± 0.07
pCi/L predicted basement mean (model SD)
0.8 ± 0.07
pCi/L predicted upstairs (above-ground) mean
1.3-1.6
range of ZIP-level basement predictions in the city
0%
of San Jose ZIPs predicted ≥ 4 pCi/L (0% ≥ 2)
What this means for San Jose
The typical San Jose home is predicted below 2 pCi/L, the lowest band. That describes the average house; the ZIP-level predictions inside the city still span 1.3 to 1.6 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 Santa Clara County as Zone 2 while the newer model predicts 1.5 pCi/L for San Jose; where they disagree, we grade on the model but show both.
Comparable California cities: Sunnyvale (1.5), Torrance (1.5), Whittier (1.5), Milpitas (1.5).
ZIP codes in San Jose
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 |
|---|---|---|---|---|
| 95037 | 9% | 1.5 ± 0.07 | 0.8 | Low |
| 95120 | 8% | 1.5 ± 0.06 | 0.8 | Low |
| 95135 | 7% | 1.5 ± 0.07 | 0.8 | Low |
| 95134 | 6% | 1.4 ± 0.08 | 0.7 | Low |
| 95138 | 6% | 1.6 ± 0.07 | 0.8 | Low |
| 95002 | 5% | 1.6 ± 0.06 | 0.8 | Low |
| 95123 | 4% | 1.5 ± 0.06 | 0.8 | Low |
| 95112 | 4% | 1.3 ± 0.09 | 0.7 | Low |
| 95125 | 4% | 1.6 ± 0.07 | 0.9 | Low |
| 95132 | 4% | 1.4 ± 0.06 | 0.8 | Low |
| 95124 | 3% | 1.5 ± 0.07 | 1.0 | Low |
| 95131 | 3% | 1.5 ± 0.06 | 0.7 | Low |
| 95111 | 3% | 1.5 ± 0.07 | 0.8 | Low |
| 95136 | 3% | 1.5 ± 0.07 | 0.8 | Low |
| 95148 | 3% | 1.4 ± 0.07 | 0.8 | Low |
| 95122 | 3% | 1.4 ± 0.07 | 0.9 | Low |
| 95127 | 3% | 1.5 ± 0.07 | 0.9 | Low |
| 95129 | 3% | 1.5 ± 0.08 | 1.0 | Low |
| 95110 | 3% | 1.4 ± 0.07 | 0.7 | Low |
| 95121 | 3% | 1.5 ± 0.07 | 0.9 | Low |
| 95118 | 2% | 1.5 ± 0.06 | 0.9 | Low |
| 95116 | 2% | 1.5 ± 0.07 | 0.8 | Low |
| 95126 | 2% | 1.3 ± 0.07 | 0.7 | Low |
| 95128 | 2% | 1.4 ± 0.07 | 0.9 | Low |
| 95133 | 2% | 1.5 ± 0.07 | 0.8 | Low |
| 95117 | 1% | 1.4 ± 0.07 | 0.9 | Low |
| 95119 | 1% | 1.5 ± 0.06 | 0.8 | Low |
| 95130 | 1% | 1.4 ± 0.07 | 0.8 | Low |
| 95139 | 1% | 1.4 ± 0.06 | 0.8 | Low |
| 95013 | 1% | — | — | no model |
| 95113 | <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.
San Jose radon questions
- Is radon high in San Jose, California?
- Low. Averaging the model's ZIP-code predictions across San Jose (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 1.5 pCi/L - about 19% 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. San Jose ranks 104 of 207 California cities on this site.
- Which San Jose ZIP codes have the highest radon?
- Predictions for the 29 modeled ZIP codes in San Jose range from 1.3 to 1.6 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 San Jose?
- Yes, once. The EPA recommends testing every home regardless of area. A short-term kit costs little and settles the question for your house; San Jose's low predicted average describes the typical home, not yours.
- What does EPA Radon Zone 2 mean for San Jose?
- San Jose sits mainly in Santa Clara 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.
← All California counties and cities · Santa Clara County · How to test · Methodology