Is Sullivan County, NH a radon risk area?

EPA's own radon map rates Sullivan County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. Sullivan County sits at the 54th percentile nationally for radon potential — above 54 of every 100 rated counties.

Where Sullivan County sits nationally

About 44,012 people live in Sullivan County, New Hampshire, spread over 537.882 square miles. Averaged across its land area, Sullivan County runs about 82 people per square mile. Rank 374 by population within its EPA zone puts Sullivan County at the 64th percentile among zone peers. Sullivan County falls in EPA Radon Region 1, one of 59 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Sullivan County

EPA's Zone 2 rating for Sullivan County sits below its own 4 pCi/L action level but above the national indoor average of about 1.3 pCi/L. Sullivan County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

Next steps for a home in Sullivan County

Nothing about Sullivan County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find New Hampshire's state radon program

Sullivan County's test kit answers today; a Airthings radon monitor keeps answering for Sullivan County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.