Radon levels in Denver, Colorado
ModerateEPA Zone 1Predicted long-term basement average of 2.1 pCi/L (model estimate) across the 29 modeled ZIP codes in Denver - about 1.2× the US average of 1.8, about 18% below the Colorado average of 2.6. Ranked #16 of 21 Colorado cities on this site. Most of the city lies in Denver County (its ZIPs also reach into 1 other county).
Test Denver, CO - the EPA says "consider fixing" in this range
The predicted basement average here is 2.1 pCi/L, in the 2-4 pCi/L band where the EPA recommends considering mitigation. Plenty of individual homes in a moderate area test above 4. Start with a short-term test; if it comes back at 2 or higher, follow up with a long-term test or a continuous monitor.
Already tested at 4 pCi/L or higher? Find a certified mitigation professional (EPA). A mitigation system typically runs $800-$2,500 installed.
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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.
2.1 ± 0.07
pCi/L predicted basement mean (model SD)
1.8 ± 0.06
pCi/L predicted upstairs (above-ground) mean
1.5-3.0
range of ZIP-level basement predictions in the city
0%
of Denver ZIPs predicted ≥ 4 pCi/L (93% ≥ 2)
What this means for Denver
The typical Denver home is predicted in the 2-4 pCi/L band. The EPA's guidance for this range is to consider fixing, because there is no known safe level and a meaningful minority of homes in a moderate area will test above 4.
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 Denver County as Zone 1 while the newer model predicts 2.1 pCi/L for Denver; where they disagree, we grade on the model but show both.
Comparable Colorado cities: Westminster (2.2), Thornton (2.1), Broomfield (2.3), Aurora (2.3).
ZIP codes in Denver
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 |
|---|---|---|---|---|
| 80249 | 32% | 1.5 ± 0.09 | 1.5 | Low |
| 80239 | 6% | 2.4 ± 0.06 | 1.8 | Moderate |
| 80219 | 5% | 2.4 ± 0.07 | 1.9 | Moderate |
| 80216 | 5% | 2.3 ± 0.05 | 1.8 | Moderate |
| 80238 | 5% | 1.5 ± 0.08 | 1.3 | Low |
| 80210 | 4% | 2.5 ± 0.06 | 2.1 | Moderate |
| 80204 | 4% | 2.4 ± 0.06 | 2.2 | Moderate |
| 80223 | 4% | 2.6 ± 0.06 | 2.1 | Moderate |
| 80220 | 3% | 2.7 ± 0.06 | 2.1 | Moderate |
| 80205 | 3% | 2.5 ± 0.06 | 1.9 | Moderate |
| 80211 | 3% | 2.3 ± 0.05 | 2.1 | Moderate |
| 80207 | 3% | 2.8 ± 0.06 | 1.8 | Moderate |
| 80237 | 2% | 3.0 ± 0.09 | 2.2 | Moderate |
| 80209 | 2% | 2.4 ± 0.06 | 1.9 | Moderate |
| 80222 | 2% | 2.8 ± 0.07 | 2.3 | Moderate |
| 80224 | 2% | 2.9 ± 0.06 | 2.0 | Moderate |
| 80236 | 2% | 2.6 ± 0.05 | 2.0 | Moderate |
| 80231 | 2% | 2.9 ± 0.06 | 2.0 | Moderate |
| 80212 | 2% | 2.3 ± 0.06 | 2.0 | Moderate |
| 80230 | 2% | 2.0 ± 0.08 | 1.6 | Moderate |
| 80206 | 2% | 2.7 ± 0.07 | 1.9 | Moderate |
| 80123 | 2% | 2.6 ± 0.07 | 2.0 | Moderate |
| 80218 | 1% | 2.5 ± 0.06 | 1.8 | Moderate |
| 80227 | 1% | 2.5 ± 0.07 | 2.1 | Moderate |
| 80247 | 1% | 2.5 ± 0.06 | 1.7 | Moderate |
| 80202 | 1% | 2.2 ± 0.05 | 1.7 | Moderate |
| 80203 | 1% | 2.4 ± 0.06 | 1.7 | Moderate |
| 80246 | 1% | 2.6 ± 0.06 | 1.8 | Moderate |
| 80235 | 1% | 2.4 ± 0.06 | 2.0 | Moderate |
| 80266 | <1% | — | — | no model |
| 80264 | <1% | — | — | no model |
| 80290 | <1% | — | — | no model |
| 80293 | <1% | — | — | no model |
| 80294 | <1% | — | — | no model |
Testing help in Colorado
Colorado's radon program page is at cdphe.colorado.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.
Denver radon questions
- Is radon high in Denver, Colorado?
- Moderate. Averaging the model's ZIP-code predictions across Denver (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 2.1 pCi/L - about 1.2× the US average of 1.8 and about 18% below the Colorado average of 2.6. That is in the 2-4 pCi/L range where the EPA says to consider fixing. Denver ranks 16 of 21 Colorado cities on this site.
- Which Denver ZIP codes have the highest radon?
- Predictions for the 29 modeled ZIP codes in Denver range from 1.5 to 3.0 pCi/L in the basement. 0% of them are predicted at or above 4 pCi/L and 93% at or above 2. That spread is why the ZIP table below matters more than the city-wide number.
- Should I test for radon in Denver?
- Yes, soon. With a predicted basement average of 2.1 pCi/L, a meaningful share of Denver homes will test above the 4 pCi/L action level. Start with a short-term kit; if it reads 2 or higher, confirm with a long-term test or a continuous monitor before paying for mitigation.
- What does EPA Radon Zone 1 mean for Denver?
- Denver sits mainly in Denver County, which the EPA classifies as Zone 1 - highest potential (predicted average > 4 pCi/L). The zone map dates from 1993 and covers whole counties. The newer model's city average of 2.1 pCi/L does not line up with Zone 1, 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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