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Radon Levels in Blaine County, Idaho

EPA puts Blaine County in Zone 1, its highest radon zone, and high results are common there: 57.7% of the 352 radon tests reported to CDC (2008 to 2017, laboratory totals) came back at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    57.7%

    16.2 pts above ID

    Blaine
    57.7%
    Idaho
    41.5%

    352 tests, 2008 to 2017

  • Median result

    5.3pCi/L

    Action level reached

    Blaine
    5.3 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    352

    9th of 37 by tests

    Blaine
    352
    Ada
    3,030

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Idaho

    9 of 37

    Top quarter

    Blaine
    57.7%
    Bear Lake
    78.1%

    By share, of 37 with 30+ tests

Read a result for Blaine County

Starts at Blaine County's median, 5.3 pCi/L

5.3pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 5.3 pCi/L

At or above 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 4 and aboveEPA says fix it

This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. Blaine County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Blaine County, At a glance

Blaine County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Blaine County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

USGS geologic potential: High across 63% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Blaine County, 2008 to 2017, laboratory

Reported results by concentration band, Blaine County, 2008 to 2017, laboratory
Under 2 pCi/L: 24%2 to 4 pCi/L: 18%4 pCi/L and above: 58%

Of 352 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Blaine County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L8624.4%
2 to 4 pCi/L6317.9%
4 pCi/L and above20357.7%
What these figures count

These are the 352 tests reported to CDC for Blaine County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.

Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Blaine County, Compared

Blaine County radon figures, compared

Calculated by Radon411

More than half: 57.7% of the 352 radon tests reported to CDC for Blaine County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 9th of 37 Idaho counties with 30 or more tests for the same period. That is 16.2 points above the 41.5% pooled from 44 Idaho counties.

The median result, 5.3 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 67.3 pCi/L. The rest split 24.4% under 2 pCi/L and 17.9% from 2 to 4 (Idaho: 31.5% and 26.9%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 57.7% share point the same way here.

2 of its 6 bordering counties with figures ran higher, led by Custer County at 72.7%; Minidoka County reported 15.3%. Statewide for the same period, Bear Lake County reported the highest share (78.1%) and Payette County the lowest (4.9%).

CDC's ten-year totals for Blaine County went from 310 tests (2005 to 2014) to 352 (2008 to 2017), the share going from 52.9% to 57.7%.

Nationally, every county with a figure for the same period pools to 35.7%; Blaine County sits 22.0 points above it. CDC also counts 16 tests taken after mitigation in Blaine County for the same period: tests in homes where a fix was already in.

Blaine County against Idaho, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Blaine County
Blaine County35257.7%5.3 pCi/LThis county
Idaho, pooled44 counties, pooled12,96141.5%Not pooled−16.2 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−22.0 points
Bear Lake Countyhighest in the state3278.1%7.8 pCi/L+20.4 points
Payette Countylowest in the state614.9%1.5 pCi/L−52.8 points
Butte County, IDborders it2975.9%12.8 pCi/L+18.2 points
Custer County, IDborders it3372.7%6.8 pCi/L+15.0 points
Cassia County, IDborders it12159.5%5.4 pCi/L+1.8 points
Bingham County, IDborders it44652.0%4.2 pCi/L−5.7 points
Elmore County, IDborders it15848.1%3.8 pCi/L−9.6 points
Lincoln County, IDborders it2040.0%3.3 pCi/L−17.7 points
Camas County, IDborders it1127.3%3.3 pCi/L−30.4 points
Power County, IDborders it4126.8%2.5 pCi/L−30.9 points
Minidoka County, IDborders it7215.3%1.8 pCi/L−42.4 points
Where Blaine County's reported results fell, 2008 to 2017, laboratory, beside Idaho and the United States
ResultBlaine County testsBlaine County shareIdaho shareU.S. shareAgainst Idaho
Under 2 pCi/L8624.4%31.5%39.6%−7.1 points
2 to 4 pCi/L6317.9%26.9%24.7%−9.0 points
4 pCi/L and above20357.7%41.5%35.7%+16.2 points
Blaine County ranked among the 37 Idaho counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Lemhi County4 of 3711265.2%5.2 pCi/L
Madison County5 of 3731463.7%6.2 pCi/L
Shoshone County6 of 378163.0%5.7 pCi/L
Kootenai County7 of 372,95561.0%6.0 pCi/L
Cassia County8 of 3712159.5%5.4 pCi/L
Blaine County9 of 3735257.7%5.3 pCi/L
Teton County10 of 3747353.3%4.4 pCi/L
Bingham County11 of 3744652.0%4.2 pCi/L
Adams County12 of 373151.6%4.0 pCi/L
Fremont County13 of 3710149.5%3.9 pCi/L
Elmore County14 of 3715848.1%3.8 pCi/L
Blaine County ten-year laboratory totals, against Idaho's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIdaho, pooledChange from the row before
2008 to 201735257.7%5.3 pCi/L67.3 pCi/L41.5%+4.3 points
2007 to 201632653.4%4.4 pCi/L67.3 pCi/L40.8%−0.4 points
2006 to 201532953.8%4.4 pCi/L67.3 pCi/L41.3%+0.9 points
2005 to 201431052.9%4.4 pCi/L75.4 pCi/L41.1%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Blaine County, Geology

The ground under Blaine County

Predicted

USGS's geologic map splits Blaine County: 63.2% of its land is high radon potential and 36.8% moderate. The map puts 63.2% of Blaine County in the area it calls Northern Rocky Mountain Province and 36.8% in Eastern Snake river plain and Malheur-Boise-King Section. USGS gives the first a radon index of 12, in the high band (12 to 17), and the second 10, in the moderate band (9 to 11).

USGS's geologic areas under Blaine County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Northern Rocky Mountain ProvinceDiorite and granite of the Idaho batholith.High1263.2%
Eastern Snake river plain and Malheur-Boise-King SectionBasalt flows.Moderate1036.8%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Blaine County beside the ground around it

Blaine County has more high-potential ground than Idaho as a whole: 63.2% of its land against 50.7%. Of the 9 counties that border it, 3 have more high-potential ground, Custer County the most at 100%.

Share of land by USGS radon potential: Blaine County, the 9 counties bordering it and Idaho
AreaEPA zoneLow potentialModerate potentialHigh potential
Blaine CountyZone 1None36.8%63.2%
Lincoln CountyZone 2None98.1%1.9%
Minidoka CountyZone 2None100%None
Butte CountyZone 1None46.9%53.1%
Camas CountyZone 1None0.2%99.8%
Cassia CountyZone 2None100%None
Custer CountyZone 1NoneNone100%
Power CountyZone 2None100%None
Bingham CountyZone 2None100%None
Elmore CountyZone 1None34.9%65.1%
Idaho44 counties, pooled by land areaVaries8.0%41.3%50.7%

The map rates the ground, not the air in any home.

Local help

Blaine County, Local resources

Radon testing and mitigation in Blaine County

What Idaho's program says
Phone
800-445-8647
Email
radon@dhw.idaho.gov

What it means

Blaine County, Questions

Questions about radon in Blaine County

Are radon levels high in Blaine County?

Over the 2008 to 2017 laboratory totals, 57.7% of the radon tests reported to CDC for Blaine County, Idaho were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.3 pCi/L. Of 37 Idaho counties with 30 or more tests for the same period, 8 reported a higher share; pooled, the state comes to 41.5%.

Which counties border Blaine County?

Blaine County borders 9 counties: Lincoln County, Minidoka County, Butte County, Camas County, Cassia County, Custer County, Power County, Bingham County and Elmore County.

Products

Blaine County, Products

Testing a home in Blaine County

In Blaine County, 57.7% of 352 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 41.5% pooled across Idaho. In Zone 1 the year-round level in Blaine County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.

Test kits and monitors3

See every kit and monitor

Blaine County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Blaine County

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Blaine County, Bordering counties

Counties bordering Blaine County

Calculated by Radon411

Blaine County, Cities and towns

Cities and towns in Blaine County

The Census Bureau estimates 25,517 residents in Blaine County for July 1, 2025, 1,176 more than in 2020 (+4.8%). Spread over its land, that is 9.7 people to the square mile. Its largest town, Hailey, has 10,053 residents, 39.4% of the total. Together its 5 incorporated places hold 73.7% of those residents; the other 26.3% live outside any of them. Testing is reported here more often than across the state: CDC's 352 reported tests for 2008 to 2017 come to 13.8 for every 1,000 residents (2025 estimate), against 6.4 for Idaho.

From Hailey to Carey, CDC publishes no figure by town: each reads Blaine County's.

The cities and towns in Blaine County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Hailey10,053+9.3%39.4%
Ketchum3,643+2.5%14.3%
Bellevue2,597+1.1%10.2%
Sun Valley1,776−0.6%7.0%
Carey727+4.9%2.8%

5 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).

Blaine County, Homes

Homes in Blaine County

Of Blaine County's 15,769 homes, 63% are detached houses, against 74% across Idaho; 17% are in buildings of five or more homes. Half of its homes were built before 1987, close to Idaho's 1990: 9% date from before 1960 and 23% from 2000 or later. Owners live in 75% of the occupied homes (Idaho: 72%), so for most households a test and a fix are their own to order.

Homes in Blaine County, Idaho, 2019 to 2023
HomesBlaine CountyIdaho
Housing units15,769776,683
Detached houses63%74%
In buildings of 5 or more17%9%
Mobile homes2%7%
Built before 19609%18%
Built since 200023%35%
Middle year built19871990
Owner-occupied75%72%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.