Radon levels in Montana

Verified county-level radon indicators are available for 51 Montana counties. Select a county for its source period and sample details.

High results are most common in Richland County (79%) and least common in Cascade County (29%)Share of tests at or above 4 pCi/L by county · Radon test results from laboratories, 2008–2017 · 51 of 56 counties have data
Beaverhead County: 59% of tests at or above 4 pCi/L · 37 testsBig Horn County: 29% of tests at or above 4 pCi/L · 21 testsBlaine County: 7% of tests at or above 4 pCi/L · 15 testsBroadwater County: 56% of tests at or above 4 pCi/L · 25 testsCarbon County: 52% of tests at or above 4 pCi/L · 46 testsCarter County: no dataCascade County: 29% of tests at or above 4 pCi/L · 235 testsChouteau County: 55% of tests at or above 4 pCi/L · 11 testsCuster County: 41% of tests at or above 4 pCi/L · 27 testsDaniels County: 0% of tests at or above 4 pCi/L · 3 testsDawson County: 47% of tests at or above 4 pCi/L · 59 testsDeer Lodge County: 31% of tests at or above 4 pCi/L · 13 testsFallon County: 63% of tests at or above 4 pCi/L · 8 testsFergus County: 72% of tests at or above 4 pCi/L · 76 testsFlathead County: 38% of tests at or above 4 pCi/L · 891 testsGallatin County: 43% of tests at or above 4 pCi/L · 1,600 testsGarfield County: no dataGlacier County: 14% of tests at or above 4 pCi/L · 7 testsGolden Valley County: no dataGranite County: 25% of tests at or above 4 pCi/L · 8 testsHill County: 15% of tests at or above 4 pCi/L · 27 testsJefferson County: 71% of tests at or above 4 pCi/L · 62 testsJudith Basin County: 64% of tests at or above 4 pCi/L · 42 testsLake County: 40% of tests at or above 4 pCi/L · 149 testsLewis and Clark County: 62% of tests at or above 4 pCi/L · 468 testsLiberty County: 33% of tests at or above 4 pCi/L · 3 testsLincoln County: 51% of tests at or above 4 pCi/L · 74 testsMcCone County: 0% of tests at or above 4 pCi/L · 1 testsMadison County: 50% of tests at or above 4 pCi/L · 58 testsMeagher County: 0% of tests at or above 4 pCi/L · 1 testsMineral County: 57% of tests at or above 4 pCi/L · 30 testsMissoula County: 45% of tests at or above 4 pCi/L · 2,613 testsMusselshell County: 29% of tests at or above 4 pCi/L · 17 testsPark County: 60% of tests at or above 4 pCi/L · 150 testsPetroleum County: no dataPhillips County: no dataPondera County: 0% of tests at or above 4 pCi/L · 5 testsPowder River County: 63% of tests at or above 4 pCi/L · 8 testsPowell County: 59% of tests at or above 4 pCi/L · 29 testsPrairie County: 67% of tests at or above 4 pCi/L · 3 testsRavalli County: 45% of tests at or above 4 pCi/L · 1,090 testsRichland County: 79% of tests at or above 4 pCi/L · 42 testsRoosevelt County: 94% of tests at or above 4 pCi/L · 16 testsRosebud County: 40% of tests at or above 4 pCi/L · 5 testsSanders County: 50% of tests at or above 4 pCi/L · 38 testsSheridan County: 76% of tests at or above 4 pCi/L · 70 testsSilver Bow County: 70% of tests at or above 4 pCi/L · 174 testsStillwater County: 56% of tests at or above 4 pCi/L · 59 testsSweet Grass County: 89% of tests at or above 4 pCi/L · 9 testsTeton County: 29% of tests at or above 4 pCi/L · 7 testsToole County: 45% of tests at or above 4 pCi/L · 11 testsTreasure County: 100% of tests at or above 4 pCi/L · 1 testsValley County: 54% of tests at or above 4 pCi/L · 24 testsWheatland County: 100% of tests at or above 4 pCi/L · 1 testsWibaux County: 50% of tests at or above 4 pCi/L · 4 testsYellowstone County: 42% of tests at or above 4 pCi/L · 1,520 tests
  • Under 10%
  • 10–20%
  • 20–30%
  • 30–40%
  • 40% or more
  • No data

Counties

CountyTests% ≥ 4 pCi/LMedian (pCi/L)EPA zone (1993)Source
Beaverhead County3759%5.0Zone 1Radon test results from laboratories through 2017
Big Horn County2129%2.0Zone 1Radon test results from laboratories through 2017
Blaine County157%1.2Zone 1Radon test results from laboratories through 2017
Broadwater County2556%4.1Zone 1Radon test results from laboratories through 2017
Carbon County4652%4.2Zone 1Radon test results from laboratories through 2017
Carter County———Zone 1—
Cascade County23529%1.7Zone 1Radon test results from laboratories through 2017
Chouteau County1155%5.5Zone 1Radon test results from laboratories through 2017
Custer County2741%3.4Zone 1Radon test results from laboratories through 2017
Daniels County30%2.5Zone 1Radon test results from laboratories through 2017
Dawson County5947%3.5Zone 1Radon test results from laboratories through 2017
Deer Lodge County1331%3.4Zone 1Radon test results from laboratories through 2017
Fallon County863%4.7Zone 1Radon test results from laboratories through 2017
Fergus County7672%7.2Zone 1Radon test results from laboratories through 2017
Flathead County89138%3.0Zone 1Radon test results from laboratories through 2017
Gallatin County1,60043%3.2Zone 1Radon test results from laboratories through 2017
Garfield County———Zone 1—
Glacier County714%2.6Zone 1Radon test results from laboratories through 2017
Golden Valley County———Zone 2—
Granite County825%2.1Zone 1Radon test results from laboratories through 2017
Hill County2715%2.1Zone 1Radon test results from laboratories through 2017
Jefferson County6271%6.3Zone 1Radon test results from laboratories through 2017
Judith Basin County4264%5.9Zone 1Radon test results from laboratories through 2017
Lake County14940%2.9Zone 1Radon test results from laboratories through 2017
Lewis and Clark County46862%5.1Zone 1Radon test results from laboratories through 2017
Liberty County333%3.8Zone 1Radon test results from laboratories through 2017
Lincoln County7451%4.0Zone 1Radon test results from laboratories through 2017
Madison County5850%3.9Zone 1Radon test results from laboratories through 2017
McCone County10%1.5Zone 1Radon test results from laboratories through 2017
Meagher County10%3.6Zone 1Radon test results from laboratories through 2017
Mineral County3057%5.1Zone 1Radon test results from laboratories through 2017
Missoula County2,61345%3.4Zone 1Radon test results from laboratories through 2017
Musselshell County1729%2.6Zone 2Radon test results from laboratories through 2017
Park County15060%5.3Zone 1Radon test results from laboratories through 2017
Petroleum County———Zone 2—
Phillips County———Zone 1—
Pondera County50%1.1Zone 1Radon test results from laboratories through 2017
Powder River County863%4.5Zone 1Radon test results from laboratories through 2017
Powell County2959%4.2Zone 1Radon test results from laboratories through 2017
Prairie County367%7.6Zone 1Radon test results from laboratories through 2017
Ravalli County1,09045%3.5Zone 1Radon test results from laboratories through 2017
Richland County4279%5.9Zone 1Radon test results from laboratories through 2017
Roosevelt County1694%8.7Zone 1Radon test results from laboratories through 2017
Rosebud County540%2.9Zone 1Radon test results from laboratories through 2017
Sanders County3850%4.0Zone 1Radon test results from laboratories through 2017
Sheridan County7076%6.5Zone 1Radon test results from laboratories through 2017
Silver Bow County17470%6.0Zone 1Radon test results from laboratories through 2017
Stillwater County5956%4.8Zone 1Radon test results from laboratories through 2017
Sweet Grass County989%11.9Zone 2Radon test results from laboratories through 2017
Teton County729%3.1Zone 1Radon test results from laboratories through 2017
Toole County1145%3.7Zone 1Radon test results from laboratories through 2017
Treasure County1100%7.5Zone 2Radon test results from laboratories through 2017
Valley County2454%4.5Zone 1Radon test results from laboratories through 2017
Wheatland County1100%12.8Zone 2Radon test results from laboratories through 2017
Wibaux County450%3.0Zone 1Radon test results from laboratories through 2017
Yellowstone County1,52042%3.4Zone 2Radon test results from laboratories through 2017

Test your home

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