New Hampshire has meaningful radon risk, with approximately 40% of New Hampshire homes estimated to have levels above the EPA action level of 4.0 pCi/L. The state’s geology — including extensive granitic bedrock — the White Mountains and Merrimack Valley granite formations create some of the highest radon potential in New England. New Hampshire’s bedrock is among the most uranium-rich in the eastern United States — creates radon potential across significant portions of the state. The Department of Health and Human Services Radiological Health Section administers radon program resources for New Hampshire residents.
EPA Radon Zone Designation
Zone 1 across most of the state due to extensive granitic geology — New Hampshire sits on the White Mountain Magma Series and Merrimack Valley granite formations.
Highest-Radon Areas in New Hampshire
Hillsborough County (Manchester, Nashua), Merrimack County (Concord), Rockingham County (Portsmouth), and Grafton County (Plymouth, Hanover) all show elevated radon levels. White Mountain counties including Carroll and Grafton have high granitic bedrock radon potential.
Radon Contractor Requirements in New Hampshire
NRPP or NRSB national certification. New Hampshire has no separate state licensing statute. The Department of Health and Human Services Radiological Health Section maintains radon program resources. Verify contractor credentials at nrpp.info or nrsb.org before engaging any radon professional for measurement or mitigation work.
Radon Disclosure in New Hampshire
New Hampshire’s real estate disclosure form requires disclosure of known material defects. Known elevated radon conditions should be disclosed. Radon testing is standard practice in New Hampshire real estate.
Testing Resources for New Hampshire Residents
Contact the Department of Health and Human Services Radiological Health Section for the most current list of certified radon professionals, any available test kit programs, and jurisdiction-specific requirements that may have been updated since this page was last reviewed. The national NRPP contractor directory (nrpp.info) is searchable by zip code and provides real-time certification verification.
Frequently Asked Questions
Is New Hampshire a high-radon state?
Yes. Approximately 40% of NH homes exceed 4.0 pCi/L — one of the highest rates in New England. NH’s granite-rich bedrock is among the most uranium-rich in the eastern U.S. Testing is essential for all NH homes.
Does New Hampshire require radon contractor licensing?
No separate NH licensing statute. NRPP or NRSB national certification is the operative credential. Search nrpp.info for certified New Hampshire contractors.
Is radon a concern in Manchester or Concord?
Yes. Hillsborough County (Manchester) and Merrimack County (Concord) are Zone 1 areas with significant radon potential. Testing is strongly recommended for all southern New Hampshire homes.
Manchester and Nashua Area Radon
Hillsborough County — New Hampshire’s most populous county, containing Manchester and Nashua — is Zone 1 with elevated radon risk throughout the county. Manchester, Nashua, Bedford, and Merrimack sit on Merrimack Valley granite formations with high uranium content. The greater Manchester-Nashua metropolitan area has among the highest residential radon testing rates in the Northeast because real estate agents and buyers in the area have long recognized radon as a standard inspection item. Rockingham County (Portsmouth area, including Salem and Derry) also shows significant Zone 1 radon levels.
White Mountains and Lakes Region Radon
Carroll County (Conway, North Conway, Wolfeboro) in the White Mountains and Lakes Region overlies the Ossipee Ring Dike — a geological formation of particular interest for radon, as ring dikes are associated with alkaline igneous rock that can have elevated uranium content. Grafton County (Plymouth, Hanover — home of Dartmouth College) is Zone 1. The White Mountains granitic formations create consistently high radon potential across the recreational and resort communities of northern New Hampshire. Second homes and vacation properties in these areas should be tested, as seasonal occupancy without testing represents an unacknowledged exposure risk.
New Hampshire Testing Resources
The New Hampshire Department of Health and Human Services (NHDHHS) Radiological Health Section administers the state radon program. NHDHHS provides certified contractor information, county-level radon survey data, and educational resources. New Hampshire participates in EPA’s SIRG program. Contact NHDHHS for the current certified contractor list. New Hampshire has historically had robust radon testing participation rates, and NHDHHS’s survey data provides detailed county-level risk information.
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