What EPA's radon map says about Richland County

EPA's own radon map rates Richland County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally, Richland County ranks higher in radon potential than 95% of rated counties (the 95th percentile).

Where Richland County sits nationally

About 124,853 people live in Richland County, Ohio, spread over 495.227 square miles. Population density there runs about 252 people per square mile. Among counties sharing Richland County's EPA zone, it outranks 85% of them by population. Geologically, Richland County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

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 — Richland County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. That doesn't mean every Richland County house tests high — a zone is a county-wide prediction, never a single-home reading — but it's a reason to test sooner rather than let it wait.

Testing and mitigation in Richland County

Mitigation cost doesn't depend on Richland 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

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

The methodology guide shows exactly which EPA and Census sources feed Richland County's numbers. Whatever zone Richland County carries, the zone explainer covers what it does and doesn't tell you about any one house.