Fairfield County, OH radon potential
Fairfield County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Fairfield County sits at the 96th percentile nationally for radon potential — above 96 of every 100 rated counties.
Where Fairfield County sits nationally
Fairfield County, Ohio is home to about 167,762 people across 504.365 square miles. Averaged across its land area, Fairfield County runs about 333 people per square mile. Within its own EPA zone, Fairfield County is bigger by population than 89% of the counties that share it. Geologically, Fairfield County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.
What this actually means for a house in Fairfield County
Where the national indoor average runs about 1.3 pCi/L, Fairfield County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Fairfield County specifically.
Testing and mitigation in Fairfield County
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 Fairfield County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Fairfield 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 Fairfield County's figures come from
Fairfield County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Fairfield County carries, the zone explainer covers what it does and doesn't tell you about any one house.