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

EPA places Rockingham County in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Rank it against the rest of the country and Rockingham County lands in the 64th percentile for radon potential.

Where Rockingham County sits nationally

Rockingham County, New Hampshire is home to about 322,433 people across 695.554 square miles. Averaged across its land area, Rockingham County runs about 464 people per square mile. By population, Rockingham County is the 70th largest of every county sharing its EPA zone — the 93rd percentile by population within that zone. Rockingham 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 Rockingham County

Call it a middle case: above the 1.3 pCi/L most US homes average, below the 4 pCi/L line EPA uses to recommend mitigation — that's Rockingham County's Zone 2 prediction. A county-wide moderate average, like Rockingham County's, can still hide a specific house well above or below it — testing is what actually answers the question.

Next steps for a home in Rockingham County

For a Rockingham 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 Rockingham County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Rockingham 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 Rockingham County's figures come from

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