Grafton County
Grafton County is classified by the EPA’s 1993 Map of Radon Zones as Zone 2, indicating moderate radon potential. The predicted average indoor radon screening level is between 2 and 4 pCi/L. While below the EPA action level, many individual homes in Zone 2 areas test above 4 pCi/L. The EPA recommends testing all homes regardless of zone.
Free Radon Test Kit for New Hampshire Homes
The New Hampshire Radon Program mails free air test kits to residents. Request one at aelabs.com/nh, or call the program at (603) 271-1708 (radon@dhhs.nh.gov). Start there before buying a kit.
Measured in New Hampshire Homes
The EPA zone above comes from a 1993 map that predicts a screening level; it is not a measured average. New Hampshire’s own data tell a different story: of 32,747 home air samples tested from 2007 to 2021, about 37% were at or above 4 pCi/L, and the state estimates the average indoor level at 5.9 pCi/L (the national average is 1.3). Results above 100 pCi/L have been reported in every county.
The state names Carroll, Rockingham and Strafford as the counties with the highest share of tested homes at or above 4 pCi/L.
These samples come from homeowners who chose to test, so they are not a random survey — but they are actual measurements. The only way to know your home’s level is to test it.
Private wells
Radon also comes from deep private wells. NH DHHS and the Department of Environmental Services recommend treating well water at or above 10,000 pCi/L (alongside air mitigation), and say treatment may be advisable between 2,000 and 10,000 pCi/L if the home’s air is at or above 4 pCi/L. Water aeration systems cost about $4,000–$6,000; air mitigation systems $1,000–$3,000.
Buying a home
Under RSA 477:4-a, a seller must give the buyer a written radon notice, which the buyer signs, before a purchase and sale agreement. The law requires notice, not a test — so ask for one.
Source: NH Department of Health and Human Services, Radon Risk in New Hampshire data brief (August 2023).
Grafton County falls into EPA Radon Zone 2, indicating moderate radon potential with predicted indoor screening levels between 2 and 4 pCi/L. It is one of 9 Zone 2 counties in New Hampshire (90% of the state's 10 counties). That is a predicted screening level from the EPA's 1993 map, not a measured average, and many individual homes in Zone 2 areas still test above it. Factors like foundation type, soil conditions, and ventilation can push radon levels higher in specific homes.
Test for radon in Grafton County
EPA Zone 2 means moderate radon potential (2-4 pCi/L predicted average). The EPA recommends testing every home; many individual Zone 2 homes test above 4 pCi/L.
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What This Means for Grafton County
Should You Test?
Yes. While Zone 2 has moderate predicted levels, many individual homes still test above 4 pCi/L. Home-specific factors like foundation type, soil permeability, and ventilation matter as much as the zone classification. A $15–$30 short-term test kit is the easiest way to find out.
Real Estate
New Hampshire law (RSA 477:4-a) requires the seller to give you a written radon notice before a purchase and sale agreement — a notice, not a test. Ask for a radon test in the home inspection; if air is at or above 4 pCi/L, mitigation typically costs $1,000–$3,000 (NH DHHS). On a private well, test the water too.
New Construction
Radon-resistant new construction (RRNC) is recommended for new homes in Zone 1 and Zone 2 areas, so if you are building here, ask your builder to include it. These features add $350–$500 to construction costs and include a sub-slab gas collection layer, vapor barrier, sealed cracks, and a vent pipe to the roof. Much cheaper to install during construction than to retrofit.