Is radon high in Boise, Idaho?

Moderate. Averaging the model's ZIP-code predictions across Boise (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. Boise ranks 5 of 9 Idaho cities on this site.

What do actual radon tests show around Boise?

Idaho Department of Health and Welfare publishes results for Ada County (not the city alone) covering through 2019 (10,189 tests): an average of 3.1 pCi/L, 22% 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 Boise is 2.4 pCi/L.

Which Boise ZIP codes have the highest radon?

Predictions for the 10 modeled ZIP codes in Boise range from 2.2 to 2.8 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 Boise?

Yes, soon. With a predicted basement average of 2.4 pCi/L, a meaningful share of Boise 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 Boise?

Boise sits mainly in Ada 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.

Radon levels in Boise, Idaho

ModerateEPA Zone 2

Predicted long-term basement average of 2.4 pCi/L (model estimate) across the 10 modeled ZIP codes in Boise - about 1.3× the US average of 1.8, close to the Idaho average of 2.6. Ranked #5 of 9 Idaho cities on this site. Most of the city lies in Ada County (its ZIPs also reach into 1 other county).

Test Boise, 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.

Get a short-term test kit →Or track it with 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 ± 0.06

pCi/L predicted basement mean (model SD)

1.7 ± 0.08

pCi/L predicted upstairs (above-ground) mean

2.2-2.8

range of ZIP-level basement predictions in the city

of Boise ZIPs predicted ≥ 4 pCi/L (100% ≥ 2)

Measured radon tests in Ada 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: 3.1 pCi/L
Results ≥ 4 pCi/L: 22%
Sample: 10,189 tests

Figure	Model (predicted)	State tests (measured)
Mean, pCi/L	2.3 basement	3.1
Share ≥ 4 pCi/L	not a model output	22%

The measured mean runs 0.8 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 Boise

The typical Boise 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 Ada and the 2001-2021 model agree here.

Comparable Idaho cities: Twin Falls (2.4), Pocatello (2.5), Idaho Falls (2.6), Coeur d'Alene (2.6).

ZIP codes in Boise

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
83716	17%	2.5 ± 0.07	1.7	Moderate
83709	14%	2.2 ± 0.05	1.6	Moderate
83705	14%	2.3 ± 0.05	1.7	Moderate
83704	11%	2.6 ± 0.05	1.8	Moderate
83702	10%	2.8 ± 0.05	2.0	Moderate
83706	9%	2.7 ± 0.07	1.9	Moderate
83713	8%	2.3 ± 0.05	1.7	Moderate
83703	7%	2.3 ± 0.05	1.8	Moderate
83712	7%	2.3 ± 0.10	1.5	Moderate
83714	4%	2.2 ± 0.05	1.3	Moderate
83725	<1%	—	—	no model
83720	<1%	—	—	no model

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.

Boise radon questions

Is radon high in Boise, Idaho?: Moderate. Averaging the model's ZIP-code predictions across Boise (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. Boise ranks 5 of 9 Idaho cities on this site.
What do actual radon tests show around Boise?: Idaho Department of Health and Welfare publishes results for Ada County (not the city alone) covering through 2019 (10,189 tests): an average of 3.1 pCi/L, 22% 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 Boise is 2.4 pCi/L.
Which Boise ZIP codes have the highest radon?: Predictions for the 10 modeled ZIP codes in Boise range from 2.2 to 2.8 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 Boise?: Yes, soon. With a predicted basement average of 2.4 pCi/L, a meaningful share of Boise 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 Boise?: Boise sits mainly in Ada 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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