Radon in Hillsborough County, New Hampshire
About 3 in 10 homes tested here were at or above the EPA action level.
- Below 2 pCi/L: 42%
- 2 to 4 pCi/L: 24%
- 4 pCi/L or more: 34%
- Median level
- 2.5 pCi/L
- EPA radon zone
- Zone 2
- In New Hampshire
- 4th of 10
EPA Zone 2, moderate radon potential (predicted average 2 to 4 pCi/L). The EPA zone map dates from 1993 and is meant for planning; high levels are found in every zone.
What to do next
Test your home
Radon levels vary between neighboring houses, so area data can't tell you your own home's level. A short-term test takes 2 to 7 days in the lowest lived-in floor. A long-term test (90 days or more) gives a more reliable average.
If your result is 4 pCi/L or more, fix it
Most homes are fixed with a sub-slab depressurization system: a pipe and a quiet fan that pull radon from under the foundation and vent it above the roof. We're still collecting real installation prices for New Hampshire.
Use a certified professional
Look for a professional certified by the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB), or by your state if it certifies radon contractors.
How Hillsborough County compares
Share of homes tested at or above 4 pCi/L, with neighboring counties. Lab data 2008–2017, the only source that covers every state.
| Rockingham County | 42% | |
|---|---|---|
| United States | 36% | |
| New Hampshire | 35% | |
| Hillsborough County | 34% | |
| Worcester County, MA | 34% | |
| Merrimack County | 31% | |
| Essex County, MA | 29% | |
| Sullivan County | 25% | |
| Middlesex County, MA | 22% | |
| Cheshire County | 20% |
Sources
- EPA Map of Radon Zones (public domain).
- CDC Environmental Public Health Tracking Network, radon tests from labs, 2008–2017. Pre-mitigation tests only.
Last updated October 2026. How we calculate these numbers.