Radon levels in Twin Falls, Idaho
ModerateEPA Zone 2Predicted long-term basement average of 2.4 pCi/L (model estimate) across the 2 modeled ZIP codes in Twin Falls - about 1.3× the US average of 1.8, close to the Idaho average of 2.6. Ranked #6 of 9 Idaho cities on this site. Most of the city lies in Twin Falls County.
Test Twin Falls, ID - the EPA says "consider fixing" in this range
The predicted basement average here is 2.4 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. Measured state test results are shown separately below, labeled with their source and years. How the numbers work.
2.4 ± 0.05
pCi/L predicted basement mean (model SD)
1.5 ± 0.05
pCi/L predicted upstairs (above-ground) mean
2.4-2.6
range of ZIP-level basement predictions in the city
0%
of Twin Falls ZIPs predicted ≥ 4 pCi/L (100% ≥ 2)
Measured radon tests in Twin Falls County (Idaho Department of Health and Welfare, through 2019)
Actual results from home radon tests reported to the state, separate from the model estimate above. Coverage: through 2019 (start year not stated by the source).
- Measured mean
- 3.0 pCi/L
- Results ≥ 4 pCi/L
- 17.4%
- Sample
- 1,458 tests
| Figure | Model (predicted) | State tests (measured) |
|---|---|---|
| Mean, pCi/L | 2.4 basement | 3.0 |
| Share ≥ 4 pCi/L | not a model output | 17.4% |
The measured mean runs 0.6 pCi/L above the model because state test data is voluntary and skews toward basements, winter, and homeowners who already suspected a problem, while the model estimates the long-term average across all homes.
Source: Home Radon Test Results by Zip Code, Idaho Department of Health and Welfare, Indoor Environment / Radon Program. No license statement on the public feature service (publicly shared by the IDHW environmental-health account). Method and download.
What this means for Twin Falls
The typical Twin Falls 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). The 1993 EPA zone (2) for Twin Falls and the 2001-2021 model agree here.
Comparable Idaho cities: Boise (2.4), Pocatello (2.5), Idaho Falls (2.6), Coeur d'Alene (2.6).
ZIP codes in Twin Falls
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.
Testing help in Idaho
Idaho's radon program page is at healthandwelfare.idaho.gov and, when we checked it, offered a free test kit (one per address every two years; listed as out of stock when checked). 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.
Twin Falls radon questions
- Is radon high in Twin Falls, Idaho?
- Moderate. Averaging the model's ZIP-code predictions across Twin Falls (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 2.4 pCi/L - about 1.3× the US average of 1.8 and close to the Idaho average of 2.6. That is in the 2-4 pCi/L range where the EPA says to consider fixing. Twin Falls ranks 6 of 9 Idaho cities on this site.
- What do actual radon tests show around Twin Falls?
- Idaho Department of Health and Welfare publishes results for Twin Falls County (not the city alone) covering through 2019 (1,458 tests): an average of 3.0 pCi/L, 17.4% of results at or above the 4 pCi/L action level. These are voluntary home tests, so they skew toward basements and toward homes where radon was suspected; the model's predicted basement average for Twin Falls is 2.4 pCi/L.
- Which Twin Falls ZIP codes have the highest radon?
- Predictions for the 2 modeled ZIP codes in Twin Falls range from 2.4 to 2.6 pCi/L in the basement. 0% of them are predicted at or above 4 pCi/L and 100% 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 Twin Falls?
- Yes, soon. With a predicted basement average of 2.4 pCi/L, a meaningful share of Twin Falls 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 2 mean for Twin Falls?
- Twin Falls sits mainly in Twin Falls 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 2001-2021 model agrees with the zone for the city. Neither replaces a test of your own home.
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