What EPA's radon map says about Knox County

EPA places Knox 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 Knox County lands in the 53rd percentile for radon potential.

Knox County by the numbers

About 40,981 people live in Knox County, Maine, spread over 364.902 square miles. That works out to roughly 112 people per square mile. Among counties sharing Knox County's EPA zone, it outranks 62% of them by population. EPA's geology-based Region 1 groups Knox County with 58 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Knox County's predicted average falls between EPA's 4 pCi/L action level and the national indoor average of about 1.3 pCi/L (outdoor air runs roughly 0.4 pCi/L). A Zone 2 rating is a moderate county-wide average, not a guarantee about any one house in Knox County — testing is the only way to know an individual home's actual level.

Next steps for a home in Knox County

Mitigation cost doesn't depend on Knox 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 Maine's state radon program

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

More on how this number was built

Knox County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.