What EPA's radon map says about Summit County

EPA places Summit 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. Summit County sits at the 99th percentile nationally for radon potential — above 99 of every 100 rated counties.

Summit County by the numbers

About 538,370 people live in Summit County, Ohio, spread over 412.686 square miles. That works out to roughly 1,305 people per square mile. Among counties sharing Summit County's EPA zone, it outranks 96% of them by population. Summit County falls in EPA Radon Region 5, one of 524 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Summit County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. A Zone 1 rating means testing is worth doing sooner rather than later, but it is still county-wide average, not a reading for any single house — some homes in Summit County will test well under the action level, and EPA's guidance is to test regardless of zone.

Next steps for a home in Summit County

Mitigation cost doesn't depend on Summit 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 Ohio's state radon program

Summit County's test kit answers today; a Airthings radon monitor keeps answering for Summit 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

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