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

EPA places Merrimack 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 Merrimack County lands in the 61st percentile for radon potential.

Merrimack County by the numbers

Merrimack County, New Hampshire is home to about 157,869 people across 932.851 square miles. Population density there runs about 169 people per square mile. By population, Merrimack County is the 146th largest of every county sharing its EPA zone — the 86th percentile by population within that zone. Merrimack County falls in EPA Radon Region 1, one of 59 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Merrimack County's Zone 2 prediction clears the 1.3 pCi/L national indoor average without reaching EPA's own 4 pCi/L point for recommending a fix. Middle-of-the-pack doesn't mean risk-free for any one Merrimack County address — a moderate county average still leaves individual homes to test either side of it.

Testing and mitigation in Merrimack County

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

Where Merrimack County's figures come from

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