What EPA's radon map says about Barnstable County

Barnstable County is mapped as Zone 2 - Moderate Potential by EPA — meaning the county-wide average indoor level is predicted between 2 and 4 pCi/L. Rank it against the rest of the country and Barnstable County lands in the 63rd percentile for radon potential.

Where Barnstable County sits nationally

About 232,570 people live in Barnstable County, Massachusetts, spread over 394.185 square miles. Population density there runs about 590 people per square mile. Among counties sharing Barnstable County's EPA zone, it outranks 90% of them by population. Barnstable 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 Barnstable County

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

If Barnstable County tests above the action level

Mitigation cost doesn't depend on Barnstable County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Massachusetts's state radon program

Barnstable County's test kit answers today; a Airthings radon monitor keeps answering for Barnstable County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

More on how this number was built

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.