Kennebec County, ME: EPA's radon zone, explained

EPA places Kennebec County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. That puts Kennebec County in the 95th percentile nationally for radon potential — higher than 95% of the counties EPA has rated.

Where Kennebec County sits nationally

Kennebec County, Maine is home to about 128,461 people across 867.507 square miles. Averaged across its land area, Kennebec County runs about 148 people per square mile. By population, Kennebec County is the 155th largest of every county sharing its EPA zone — the 86th percentile by population within that zone. Kennebec County falls in EPA Radon Region 1, one of 59 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Kennebec County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. Being in Zone 1 raises the odds Kennebec County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

Testing and mitigation in Kennebec County

For a Kennebec 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 Maine's state radon program

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

Where Kennebec 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. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.