What EPA's radon map says about Buncombe County

EPA places Buncombe 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. Nationally, Buncombe County ranks higher in radon potential than 97% of rated counties (the 97th percentile).

Where Buncombe County sits nationally

About 279,210 people live in Buncombe County, North Carolina, spread over 656.49 square miles. Population density there runs about 425 people per square mile. Among counties sharing Buncombe County's EPA zone, it outranks 92% of them by population. EPA's geology-based Region 4 groups Buncombe County with 735 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Buncombe County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. Some Buncombe County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

Testing and mitigation in Buncombe County

Mitigation cost doesn't depend on Buncombe 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 North Carolina's state radon program

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

More on how this number was built

Buncombe County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Buncombe County carries, the zone explainer covers what it does and doesn't tell you about any one house.