Hamilton County, OH radon potential
EPA's own radon map rates Hamilton County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally that's the 100th percentile for radon potential — Hamilton County outranks 100% of every county EPA has rated.
Hamilton County by the numbers
Hamilton County, Ohio is home to about 837,359 people across 405.454 square miles. Averaged across its land area, Hamilton County runs about 2,065 people per square mile. Within its own EPA zone, Hamilton County is bigger by population than 99% of the counties that share it. EPA's geology-based Region 5 groups Hamilton County with 523 other counties nationally sharing its underlying rock and soil profile.
Zone vs. an actual test
Hamilton 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. That doesn't mean every Hamilton 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.
Next steps for a home in Hamilton 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 Hamilton County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Hamilton County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.
Where Hamilton County's figures come from
Hamilton County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Hamilton County carries, the zone explainer covers what it does and doesn't tell you about any one house.