Jefferson County, OH radon potential

EPA's own radon map rates Jefferson County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Jefferson County sits at the 92nd percentile nationally for radon potential — above 92 of every 100 rated counties.

How Jefferson County compares

Jefferson County, Ohio is home to about 63,900 people across 408.124 square miles. Population density there runs about 157 people per square mile. Within its own EPA zone, Jefferson County is bigger by population than 76% of the counties that share it. EPA's geology-based Region 5 groups Jefferson County with 523 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Jefferson County carries a Zone 1 label because its predicted average clears 4 pCi/L outright — three-plus times the 0.4 pCi/L typical outdoors and above the 1.3 pCi/L most homes see. Being in Zone 1 raises the odds Jefferson 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.

If Jefferson County tests above the action level

A short-term test kit is the standard first step and typically costs far less than mitigation itself. If a test comes back at or above 4 pCi/L, a radon mitigation system for a typical home runs roughly $800–$2,500 (around $1,200 for a common single-family install), driven mainly by foundation type, not by county.

Find Ohio's state radon program

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

Where Jefferson County's figures come from

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