Radon levels in New Hampshire

Verified county-level radon indicators are available for 10 New Hampshire counties. Select a county for its source period and sample details.

High results are most common in Carroll County (48%) and least common in Cheshire County (20%)Share of tests at or above 4 pCi/L by county · Radon test results from laboratories, 2008–2017 · 10 of 10 counties have data
Belknap County: 32% of tests at or above 4 pCi/L · 385 testsCarroll County: 48% of tests at or above 4 pCi/L · 425 testsCheshire County: 20% of tests at or above 4 pCi/L · 952 testsCoos County: 34% of tests at or above 4 pCi/L · 362 testsGrafton County: 26% of tests at or above 4 pCi/L · 1,579 testsHillsborough County: 34% of tests at or above 4 pCi/L · 5,528 testsMerrimack County: 31% of tests at or above 4 pCi/L · 1,179 testsRockingham County: 42% of tests at or above 4 pCi/L · 4,077 testsStrafford County: 43% of tests at or above 4 pCi/L · 870 testsSullivan County: 25% of tests at or above 4 pCi/L · 251 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
Belknap County38532%2.3Zone 2Radon test results from laboratories through 2017
Carroll County42548%3.5Zone 1Radon test results from laboratories through 2017
Cheshire County95220%1.8Zone 2Radon test results from laboratories through 2017
Coos County36234%2.3Zone 2Radon test results from laboratories through 2017
Grafton County1,57926%2.2Zone 2Radon test results from laboratories through 2017
Hillsborough County5,52834%2.5Zone 2Radon test results from laboratories through 2017
Merrimack County1,17931%2.1Zone 2Radon test results from laboratories through 2017
Rockingham County4,07742%3.1Zone 2Radon test results from laboratories through 2017
Strafford County87043%3.1Zone 2Radon test results from laboratories through 2017
Sullivan County25125%2.3Zone 2Radon test results from laboratories through 2017

Test your home

County figures show how often tests come back high, not the level in your home. Only a test tells you that: see how to test for radon.

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