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

Nantucket 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. Nationally that's the 43rd percentile for radon potential — Nantucket County outranks 43% of every county EPA has rated.

Where Nantucket County sits nationally

Nantucket County, Massachusetts is home to about 14,670 people across 46.192 square miles. Population density there runs about 318 people per square mile. By population, Nantucket County is the 720th largest of every county sharing its EPA zone — the 30th percentile by population within that zone. Nantucket 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

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Nantucket County's Zone 2 prediction lands in the gap between the two. A Zone 2 rating is a moderate county-wide average, not a guarantee about any one house in Nantucket County — testing is the only way to know an individual home's actual level.

Next steps for a home in Nantucket County

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

Where Nantucket 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. Whatever zone Nantucket County carries, the zone explainer covers what it does and doesn't tell you about any one house.