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Radon Levels in Elmore County, Idaho

EPA puts Elmore County in Zone 1, its highest radon zone, and high results are common there: 48.1% of the 158 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

    48.1%

    6.6 pts above ID

    Elmore
    48.1%
    Idaho
    41.5%

    158 tests, 2008 to 2017

  • Median result

    3.8pCi/L

    Below action level

    Elmore
    3.8 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    158

    13th of 37 by tests

    Elmore
    158
    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

    14 of 37

    Middle half

    Elmore
    48.1%
    Bear Lake
    78.1%

    By share, of 37 with 30+ tests

Read a result for Elmore County

Starts at Elmore County's median, 3.8 pCi/L

3.8pCi/L

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

EPA’s reading of 3.8 pCi/L

Between 2 and 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 between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Elmore County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Elmore County, At a glance

Elmore County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Elmore 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 65% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

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

Reported results by concentration band, Elmore County, 2008 to 2017, laboratory
Under 2 pCi/L: 29%2 to 4 pCi/L: 23%4 pCi/L and above: 48%

Of 158 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Elmore County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L4528.5%
2 to 4 pCi/L3723.4%
4 pCi/L and above7648.1%
What these figures count

These are the 158 tests reported to CDC for Elmore 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

Elmore County, Compared

Elmore County radon figures, compared

Calculated by Radon411

In Elmore County, about 5 in 10 reported tests over the 2008 to 2017 laboratory totals (76 of 158) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 12.4 points higher. Across 44 Idaho counties pooled together, 41.5% of tests reached that level, so Elmore County runs 6.6 points above its state.

Of 7 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 5 a smaller one; the spread is 22.4% (Boise County) to 72.7% (Custer County). By share, Elmore County is 14th of 37 Idaho counties with 30 or more tests for the same period.

Half the tests came in under 3.8 pCi/L and half over it; the single highest reached 94.3 pCi/L. Below the action level, 45 tests (28.5%) came in under 2 pCi/L, against 31.5% statewide, and 37 tests (23.4%) fell between 2 and 4, against 26.9% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 48.1% share point the same way here. USGS geology rates 65% of the county's land high radon potential. CDC also counts 9 tests taken after mitigation in Elmore County for the same period: tests in homes where a fix was already in.

CDC's ten-year totals for Elmore County went from 165 tests (2005 to 2014) to 158 (2008 to 2017), the share going from 49.7% to 48.1%.

Elmore County against Idaho, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Elmore County
Elmore County15848.1%3.8 pCi/LThis county
Idaho, pooled44 counties, pooled12,96141.5%Not pooled−6.6 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−12.4 points
Bear Lake Countyhighest in the state3278.1%7.8 pCi/L+30.0 points
Payette Countylowest in the state614.9%1.5 pCi/L−43.2 points
Custer County, IDborders it3372.7%6.8 pCi/L+24.6 points
Blaine County, IDborders it35257.7%5.3 pCi/L+9.6 points
Gooding County, IDborders it6728.4%2.4 pCi/L−19.7 points
Camas County, IDborders it1127.3%3.3 pCi/L−20.8 points
Ada County, IDborders it3,03025.2%2.4 pCi/L−22.9 points
Twin Falls County, IDborders it36924.1%2.4 pCi/L−24.0 points
Owyhee County, IDborders it3023.3%2.1 pCi/L−24.8 points
Boise County, IDborders it5822.4%2.0 pCi/L−25.7 points
Where Elmore County's reported results fell, 2008 to 2017, laboratory, beside Idaho and the United States
ResultElmore County testsElmore County shareIdaho shareU.S. shareAgainst Idaho
Under 2 pCi/L4528.5%31.5%39.6%−3.0 points
2 to 4 pCi/L3723.4%26.9%24.7%−3.5 points
4 pCi/L and above7648.1%41.5%35.7%+6.6 points
Elmore 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
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
Caribou County15 of 375743.9%3.4 pCi/L
Bannock County16 of 3773241.9%3.2 pCi/L
Bonneville County17 of 371,11740.1%3.4 pCi/L
Idaho County18 of 379040.0%2.9 pCi/L
Franklin County19 of 377534.7%3.1 pCi/L
Elmore County ten-year laboratory totals, against Idaho's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIdaho, pooledChange from the row before
2008 to 201715848.1%3.8 pCi/L94.3 pCi/L41.5%+0.6 points
2007 to 201616247.5%3.5 pCi/L94.3 pCi/L40.8%−1.1 points
2006 to 201518548.6%3.9 pCi/L94.3 pCi/L41.3%−1.1 points
2005 to 201416549.7%3.9 pCi/L94.3 pCi/L41.1%First on file

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

Elmore County, Geology

The ground under Elmore County

Predicted

USGS's geologic map splits Elmore County: 65.1% of its land is high radon potential and 34.9% moderate. The map puts 65.1% of Elmore County in the area it calls Northern Rocky Mountain Province and 34.9% 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 Elmore County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Northern Rocky Mountain ProvinceDiorite and granite of the Idaho batholith.High1265.1%
Eastern Snake river plain and Malheur-Boise-King SectionBasalt flows.Moderate1034.9%

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

Elmore County beside the ground around it

Elmore County has more high-potential ground than Idaho as a whole: 65.1% of its land against 50.7%. Of the 8 counties that border it, 3 have more high-potential ground, Custer County the most at 100%.

Share of land by USGS radon potential: Elmore County, the 8 counties bordering it and Idaho
AreaEPA zoneLow potentialModerate potentialHigh potential
Elmore CountyZone 1None34.9%65.1%
Ada CountyZone 2None88.6%11.4%
Camas CountyZone 1None0.2%99.8%
Boise CountyZone 10.1%None99.9%
Gooding CountyZone 1None46.2%53.8%
Owyhee CountyZone 2None100%None
Twin Falls CountyZone 2None100%None
Blaine CountyZone 1None36.8%63.2%
Custer CountyZone 1NoneNone100%
Idaho44 counties, pooled by land areaVaries8.0%41.3%50.7%

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

Local help

Elmore County, Local resources

Radon testing and mitigation in Elmore County

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

What it means

Elmore County, Questions

Questions about radon in Elmore County

Are radon levels high in Elmore County?

Over the 2008 to 2017 laboratory totals, 48.1% of the radon tests reported to CDC for Elmore County, Idaho were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.8 pCi/L. Of 37 Idaho counties with 30 or more tests for the same period, 13 reported a higher share; pooled, the state comes to 41.5%.

Which counties border Elmore County?

Elmore County borders 8 counties: Ada County, Camas County, Boise County, Gooding County, Owyhee County, Twin Falls County, Blaine County and Custer County.

Products

Elmore County, Products

Testing a home in Elmore County

In Elmore County, 48.1% of 158 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 Elmore 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

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

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Elmore County, Bordering counties

Counties bordering Elmore County

Calculated by Radon411

Elmore County, Cities and towns

Cities and towns in Elmore County

The Census Bureau estimates 29,465 residents in Elmore County for July 1, 2025, 795 more than in 2020 (+2.8%). Spread over its land, that is 9.6 people to the square mile. Mountain Home alone is home to 16,779 of them, 56.9% of the total. Together its 2 incorporated places hold 61.2% of those residents; the other 38.8% live outside any of them. CDC's 158 reported tests for 2008 to 2017 work out to 5.4 per 1,000 residents (2025 estimate), close to Idaho's 6.4.

From Mountain Home to Glenns Ferry, CDC publishes no figure by town: each reads Elmore County's.

The cities and towns in Elmore County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Mountain Home16,779+4.5%56.9%
Glenns Ferry1,256−1.9%4.3%

2 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).

Elmore County, Homes

Homes in Elmore County

Of Elmore County's 12,168 homes, 70% are detached houses, against 74% across Idaho; 12% are mobile homes. Half of its homes were built before 1985, close to Idaho's 1990: 15% date from before 1960 and 29% from 2000 or later. 65% of occupied homes are lived in by their owner (Idaho: 72%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Elmore County, Idaho, 2019 to 2023
HomesElmore CountyIdaho
Housing units12,168776,683
Detached houses70%74%
In buildings of 5 or more3%9%
Mobile homes12%7%
Built before 196015%18%
Built since 200029%35%
Middle year built19851990
Owner-occupied65%72%

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