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

EPA's own radon map rates Preble County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally, Preble County ranks higher in radon potential than 88% of rated counties (the 88th percentile).

Preble County by the numbers

Preble County, Ohio is home to about 40,801 people across 424.226 square miles. Averaged across its land area, Preble County runs about 96 people per square mile. By population, Preble County is the 374th largest of every county sharing its EPA zone — the 65th percentile by population within that zone. EPA's geology-based Region 5 groups Preble County with 523 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Preble County

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Preble County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. 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 Preble County will test well under the action level, and EPA's guidance is to test regardless of zone.

Testing and mitigation in Preble County

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

Where Preble County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Preble County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.