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Radon Levels in Owyhee County, Idaho

EPA puts Owyhee County in Zone 2, its middle radon zone, and 23.3% of its 30 reported radon tests (2008 to 2017, laboratory totals) were 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

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  • Share at 4+ pCi/L

    23.3%

    18.2 pts below ID

    Owyhee
    23.3%
    Idaho
    41.5%

    30 tests, 2008 to 2017

  • Median result

    2.1pCi/L

    Below action level

    Owyhee
    2.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    30

    37th of 37 by tests

    Owyhee
    30
    Ada
    3,030

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in Idaho

    28 of 37

    Middle half

    Owyhee
    23.3%
    Bear Lake
    78.1%

    By share, of 37 with 30+ tests

Read a result for Owyhee County

Starts at Owyhee County's median, 2.1 pCi/L

2.1pCi/L

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

EPA’s reading of 2.1 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. Owyhee County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Owyhee County, At a glance

Owyhee County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Owyhee County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

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

Reported results by concentration band, Owyhee County, 2008 to 2017, laboratory
Under 2 pCi/L: 47%2 to 4 pCi/L: 30%4 pCi/L and above: 23%

Of 30 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Owyhee County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L1446.7%
2 to 4 pCi/L930.0%
4 pCi/L and above723.3%
What these figures count

These are the 30 tests reported to CDC for Owyhee 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

Owyhee County, Compared

Owyhee County radon figures, compared

Calculated by Radon411

Owyhee County's 30 reported tests over the 2008 to 2017 laboratory totals had a middle value of 2.1 pCi/L and a maximum of 8.4 pCi/L, and 23.3% reached 4 pCi/L. Idaho as a whole (44 Idaho counties, pooled) comes to 41.5%: 18.2 points higher than here.

Among its state's counties it ranks 28th of 37 Idaho counties with 30 or more tests for the same period. Statewide for the same period, Bear Lake County reported the highest share (78.1%) and Payette County the lowest (4.9%).

Below the action level, 14 tests (46.7%) came in under 2 pCi/L, against 31.5% statewide, and 9 tests (30.0%) fell between 2 and 4, against 26.9% statewide. CDC's ten-year totals for Owyhee County went from 37 tests (2005 to 2014) to 30 (2008 to 2017), the share going from 21.6% to 23.3%.

EPA's 1993 zone map puts Owyhee County in Zone 2, a predicted county average between 2 and 4 pCi/L. USGS geology rates 100% of the county's land moderate radon potential.

Next door, the shares run from 10.7% in Canyon County to 48.1% in Elmore County, with Canyon County below Owyhee County.

Owyhee County against Idaho, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Owyhee County
Owyhee County3023.3%2.1 pCi/LThis county
Idaho, pooled44 counties, pooled12,96141.5%Not pooled+18.2 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+54.8 points
Payette Countylowest in the state614.9%1.5 pCi/L−18.4 points
Elmore County, IDborders it15848.1%3.8 pCi/L+24.8 points
Elko County, NVborders it15940.3%3.1 pCi/L+17.0 points
Humboldt County, NVborders it6532.3%2.3 pCi/L+9.0 points
Ada County, IDborders it3,03025.2%2.4 pCi/L+1.9 points
Twin Falls County, IDborders it36924.1%2.4 pCi/L+0.8 points
Canyon County, IDborders it56310.7%1.6 pCi/L−12.6 points
Malheur County, ORborders it128.3%2.0 pCi/L−15.0 points
Where Owyhee County's reported results fell, 2008 to 2017, laboratory, beside Idaho and the United States
ResultOwyhee County testsOwyhee County shareIdaho shareU.S. shareAgainst Idaho
Under 2 pCi/L1446.7%31.5%39.6%+15.2 points
2 to 4 pCi/L930.0%26.9%24.7%+3.1 points
4 pCi/L and above723.3%41.5%35.7%−18.2 points
Owyhee 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
Valley County23 of 3712827.3%2.3 pCi/L
Power County24 of 374126.8%2.5 pCi/L
Latah County25 of 3715026.0%1.7 pCi/L
Ada County26 of 373,03025.2%2.4 pCi/L
Twin Falls County27 of 3736924.1%2.4 pCi/L
Owyhee County28 of 373023.3%2.1 pCi/L
Boise County29 of 375822.4%2.0 pCi/L
Nez Perce County30 of 3714922.1%2.3 pCi/L
Washington County31 of 376720.9%2.1 pCi/L
Gem County32 of 379920.2%1.9 pCi/L
Boundary County33 of 374520.0%2.1 pCi/L
Owyhee County ten-year laboratory totals, against Idaho's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIdaho, pooledChange from the row before
2008 to 20173023.3%2.1 pCi/L8.4 pCi/L41.5%+3.3 points
2007 to 20163520.0%1.8 pCi/L8.4 pCi/L40.8%−2.2 points
2006 to 20153622.2%1.9 pCi/L8.4 pCi/L41.3%+0.6 points
2005 to 20143721.6%1.8 pCi/L8.4 pCi/L41.1%First on file

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

Owyhee County, Geology

The ground under Owyhee County

Predicted

USGS's geologic map puts all of Owyhee County's mapped land in one class: moderate radon potential. The map puts 82.6% of Owyhee County in the area it calls Owyhee Upland and 17.4% in Eastern Snake river plain and Malheur-Boise-King Section. USGS gives the first a radon index of 9 and the second 10, both in the moderate band (9 to 11).

USGS's geologic areas under Owyhee County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Owyhee UplandTertiary and Quaternary basalt, andesite, and rhyolite.Moderate982.6%
Eastern Snake river plain and Malheur-Boise-King SectionBasalt flows.Moderate1017.4%

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

Owyhee County beside the ground around it

Across Idaho 50.7% of the land is rated high; none of Owyhee County's is. Of the 7 counties that border it, 5 have more high-potential ground, Elmore County the most at 65.1%.

Share of land by USGS radon potential: Owyhee County, the 7 counties bordering it and Idaho
AreaEPA zoneLow potentialModerate potentialHigh potential
Owyhee CountyZone 2None100%None
Ada CountyZone 2None88.6%11.4%
Elmore CountyZone 1None34.9%65.1%
Canyon CountyZone 2None100%None
Malheur County, ORZone 20.2%99.6%0.2%
Twin Falls CountyZone 2None100%None
Elko County, NVZone 2None88.5%11.5%
Humboldt County, NVZone 2None74.8%25.2%
Idaho44 counties, pooled by land areaVaries8.0%41.3%50.7%

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

Local help

Owyhee County, Local resources

Radon testing and mitigation in Owyhee County

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

What it means

Owyhee County, Questions

Questions about radon in Owyhee County

Are radon levels high in Owyhee County?

Over the 2008 to 2017 laboratory totals, 23.3% of the radon tests reported to CDC for Owyhee County, Idaho were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.1 pCi/L. Of 37 Idaho counties with 30 or more tests for the same period, 27 reported a higher share; pooled, the state comes to 41.5%.

Which counties border Owyhee County?

Owyhee County borders 7 counties: Ada County, ID, Elmore County, ID, Canyon County, ID, Malheur County, OR, Twin Falls County, ID, Elko County, NV and Humboldt County, NV.

Products

Owyhee County, Products

Testing a home in Owyhee County

In Owyhee County, 23.3% of 30 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 41.5% pooled across Idaho. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Owyhee County; a long-term test tells the year-round average.

Test kits and monitors3

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Best radon monitors for Owyhee County homes, compared

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Owyhee County, Bordering counties

Counties bordering Owyhee County

Calculated by Radon411

Owyhee County, Cities and towns

Cities and towns in Owyhee County

Owyhee County is growing: the Census Bureau puts it at 12,661 residents on July 1, 2025, up 5.6% from 11,993 in 2020. Spread over its land, that is 1.7 people to the square mile. Its largest town, Homedale, has 3,138 residents, 24.8% of the total. Together its 3 incorporated places hold 38.1% of those residents; the other 61.9% live outside any of them. Reported testing is thin here: 30 tests over 2008 to 2017, or 2.4 for every 1,000 residents (2025 estimate), where Idaho as a whole comes to 6.4.

From Homedale to Grand View, CDC publishes no figure by town: each reads Owyhee County's.

The cities and towns in Owyhee County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Homedale3,138+7.6%24.8%
Marsing1,230+0.1%9.7%
Grand View461+3.6%3.6%

3 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).

Owyhee County, Homes

Homes in Owyhee County

Of Owyhee County's 4,803 homes, 71% are detached houses, against 74% across Idaho; 22% are mobile homes. The homes are older than Idaho's as a whole: half were built before 1982 (1990 for Idaho), and 23% date from before 1960. 71% 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 Owyhee County, Idaho, 2019 to 2023
HomesOwyhee CountyIdaho
Housing units4,803776,683
Detached houses71%74%
In buildings of 5 or more3%9%
Mobile homes22%7%
Built before 196023%18%
Built since 200028%35%
Middle year built19821990
Owner-occupied71%72%

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