Norfolk County, MA: EPA's radon zone, explained

EPA places Norfolk 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 Norfolk County lands in the 65th percentile for radon potential.

Norfolk County by the numbers

Norfolk County, Massachusetts is home to about 740,754 people across 396.103 square miles. Population density there runs about 1,870 people per square mile. By population, Norfolk County is the 31st largest of every county sharing its EPA zone — the 97th percentile by population within that zone. EPA's geology-based Region 1 groups Norfolk County with 58 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

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

Testing and mitigation in Norfolk County

For a Norfolk 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 Massachusetts's state radon program

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

Where Norfolk County's figures come from

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.