Carroll County, NH: EPA's radon zone, explained

Carroll County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. That puts Carroll County in the 90th percentile nationally for radon potential — higher than 90% of the counties EPA has rated.

How Carroll County compares

Carroll County, New Hampshire is home to about 52,580 people across 931.876 square miles. That works out to roughly 56 people per square mile. By population, Carroll County is the 302nd largest of every county sharing its EPA zone — the 72nd percentile by population within that zone. EPA's geology-based Region 1 groups Carroll County with 58 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Carroll County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Some Carroll County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

Testing and mitigation in Carroll County

For a Carroll County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find New Hampshire's state radon program

For Carroll County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Carroll County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

Where Carroll County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Carroll County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.