Allen County, OH: EPA's radon zone, explained

EPA's own radon map rates Allen County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Allen County sits at the 94th percentile nationally for radon potential — above 94 of every 100 rated counties.

How Allen County compares

Allen County, Ohio is home to about 100,866 people across 402.545 square miles. That works out to roughly 251 people per square mile. By population, Allen County is the 193rd largest of every county sharing its EPA zone — the 82nd percentile by population within that zone. EPA's geology-based Region 5 groups Allen County with 523 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Allen County

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Allen County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Being in Zone 1 raises the odds Allen 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.

Next steps for a home in Allen County

For a Allen 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 Ohio's state radon program

For Allen County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Allen 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 Allen County's figures come from

Allen 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.