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Radon Levels, Testing and Mitigation in Idaho

Idaho has 44 counties, with 19 classified as EPA Zone 1 (highest risk). With an average radon level of 8.67 pCi/L, Idaho state testing data reveals significantly elevated risks across multiple counties. Testing is highly recommended.

Idaho is the 14th most expansive state and the 39th most populous. It also happens to be the seventh least densely populated state in the entire US.

The state has a radon program, dedicated to educating citizens about the risks associated with the deadly gas. You can find more information on Radon, testing and mitigation at the official Idaho government page.

8.67
Avg. pCi/L
44
Counties
19
Zone 1 Counties

Idaho Radon Map

Idaho radon levels by county
Zone 1 — High
Zone 2 — Moderate
Zone 3 — Low

Idaho Metro Areas

Explore radon data organized by metro region, including average levels, hotspot cities, and local mitigation professionals.

Boise Metro
5 cities
Coeur d'Alene Metro
5 cities
Idaho Falls Metro
5 cities
Logan Metro
5 cities

Most Active Radon Markets in Idaho

Cities with the most user-submitted radon test data, ranked by number of submissions.

CityAvg User Radon LevelSubmissions
Idaho Falls 7.29 pCi/L 7
Hailey 7.83 pCi/L 6
Post Falls 9.00 pCi/L 5
Coeur D Alene 9.00 pCi/L 4
Moscow 7.75 pCi/L 4
Victor 6.67 pCi/L 3
Driggs 16.00 pCi/L 2
Hayden 8.50 pCi/L 2
Pocatello 8.50 pCi/L 2
Eagle 6.00 pCi/L 1
Boise No submissions 0
Nampa No submissions 0
Sandpoint No submissions 0

Idaho Counties by EPA Radon Zone

All 44 Idaho counties with their EPA radon zone classification and user-submitted average radon levels.

Zone 1 — High Risk
Predicted avg. indoor levels > 4.0 pCi/L
Zone 1 19 counties
Benewah County Zone 1
Avg:
Blaine County Zone 1
Avg: 9.9 pCi/L
Boise County Zone 1
Avg:
Bonner County Zone 1
Avg: 4.3 pCi/L
Boundary County Zone 1
Avg: 5.0 pCi/L
Butte County Zone 1
Avg:
Camas County Zone 1
Avg:
Clark County Zone 1
Avg:
Clearwater County Zone 1
Avg:
Custer County Zone 1
Avg:
Elmore County Zone 1
Avg:
Fremont County Zone 1
Avg: 20.0 pCi/L
Gooding County Zone 1
Avg:
Idaho County Zone 1
Avg:
Kootenai County Zone 1
Avg: 10.1 pCi/L
Latah County Zone 1
Avg: 7.8 pCi/L
Lemhi County Zone 1
Avg:
Shoshone County Zone 1
Avg: 14.0 pCi/L
Valley County Zone 1
Avg: 4.0 pCi/L
Zone 2 — Moderate Risk
Predicted avg. indoor levels 2–4 pCi/L
Zone 2 20 counties
Ada County Zone 2
Avg: 6.0 pCi/L
Bannock County Zone 2
Avg: 8.5 pCi/L
Bear Lake County Zone 2
Avg: 4.0 pCi/L
Bingham County Zone 2
Avg: 8.5 pCi/L
Bonneville County Zone 2
Avg: 7.3 pCi/L
Canyon County Zone 2
Avg:
Caribou County Zone 2
Avg: 13.0 pCi/L
Cassia County Zone 2
Avg: 2.0 pCi/L
Franklin County Zone 2
Avg:
Jefferson County Zone 2
Avg:
Jerome County Zone 2
Avg:
Lincoln County Zone 2
Avg:
Madison County Zone 2
Avg:
Minidoka County Zone 2
Avg:
Oneida County Zone 2
Avg: 6.0 pCi/L
Owyhee County Zone 2
Avg:
Payette County Zone 2
Avg:
Power County Zone 2
Avg:
Teton County Zone 2
Avg: 10.4 pCi/L
Twin Falls County Zone 2
Avg:
Zone 3 — Low Risk
Predicted avg. indoor levels < 2 pCi/L
Zone 3 5 counties
Adams County Zone 3
Avg: 5.0 pCi/L
Gem County Zone 3
Avg:
Lewis County Zone 3
Avg: 3.0 pCi/L
Nez Perce County Zone 3
Avg:
Washington County Zone 3
Avg:

Idaho Cities & Towns

Browse radon data for individual cities across Idaho. Each city page includes user-submitted radon levels, local contractors, and mitigation resources.

Aberdeen Ahsahka Albion American Falls Arbon Arco Arimo Ashton Athol Atomic City Avery Bancroft Banks Bayview Bellevue Bern Blackfoot Blanchard Bliss Boise Bonners Ferry Bruneau Buhl Burley Calder Caldwell Cambridge Carey Careywood Carmen Cascade Castleford Cataldo Challis Clark Fork Clarkia Clayton Clifton Cobalt Cocolalla Coeur D Alene Conda Coolin Corral Cottonwood Council Craigmont Culdesac Dayton Deary Declo Desmet Dietrich Donnelly Downey Driggs Dubois Eagle Eden Elk City Ellis Emmett Fairfield Felt Ferdinand Fernwood Filer Firth Fish Haven Franklin Fruitland Garden City Garden Valley Genesee Geneva Gibbonsville Glenns Ferry Gooding Grace Grand View Grangeville Greencreek Greenleaf Hagerman Hailey Hamer Hammett Hansen Harrison Harvard Hayden Hazelton Heyburn Holbrook Homedale Hope Horseshoe Bend Howe Idaho City Idaho Falls Indian Valley Inkom Iona Irwin Island Park Jerome Juliaetta Kamiah Kellogg Kendrick Ketchum Kimberly King Hill Kingston Kooskia Kuna Lapwai Lava Hot Springs Leadore Lenore Lewiston Lewisville Lowman Lucile Mackay Malad City Malta Marsing May Mccall Mccammon Medimont Melba Menan Meridian Mesa Middleton Midvale Monteview Montpelier Moore Moscow Mountain Home Mountain Home A F B Moyie Springs Mullan Murphy Murtaugh Nampa Naples New Meadows New Plymouth Newdale Nezperce Nordman North Fork Oakley Ola Oldtown Orofino Parma Paul Payette Peck Picabo Pierce Pinehurst Pingree Placerville Plummer Pocatello Pollock Ponderay Porthill Post Falls Potlatch Preston Priest River Princeton Rathdrum Reubens Rexburg Richfield Rigby Riggins Ririe Roberts Rockland Rogerson Rupert Sagle Saint Anthony Saint Charles Saint Maries Salmon Sandpoint Shelley Shoshone Shoup Smelterville Soda Springs Spencer Spirit Lake Springfield Stanley Star Stites Sugar City Swan Valley Sweet Tensed Terreton Teton Tetonia Thatcher Troy Twin Falls Victor Viola Wallace Wayan Weippe Weiser Wendell Weston White Bird Wilder Winchester Worley Yellow Pine

Frequently Asked Questions About Radon in Idaho

What radon level is considered "high"?
The EPA action level is 4.0 pCi/L — many homeowners also choose to fix levels between 2.0 and 4.0 pCi/L. Any home with levels at or above 4.0 pCi/L should be mitigated.
How much does radon mitigation cost in Idaho?
Radon mitigation typically costs between $800 and $2,500, depending on foundation type and radon severity. A standard sub-slab depressurization system usually falls in the $1,000–$1,500 range.
Does mitigation actually work?
Yes — properly installed systems typically reduce radon levels by up to 99%. A post-mitigation test confirms the system is working correctly, and many homeowners re-test periodically.
Should I test again after mitigation?
Yes. A post-mitigation test is the proof your system is working. The EPA recommends testing within 30 days of installation and retesting every two years.
What EPA Radon Zone is my Idaho county in?
Idaho counties are classified into three EPA Radon Zones. Zone 1 (highest risk, >4 pCi/L) indicates the most concern. Zone 2 (moderate, 2–4 pCi/L) and Zone 3 (lowest, <2 pCi/L) round out the classification. Use the county directory above to find your specific county's zone and data.

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