Hamilton County, IN 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 98th percentile for radon potential — Hamilton County outranks 98% of every county EPA has rated.
Hamilton County by the numbers
Hamilton County, Indiana is home to about 379,704 people across 394.39 square miles. That works out to roughly 963 people per square mile. Within its own EPA zone, Hamilton County is bigger by population than 94% 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.
What this actually means for a house in Hamilton County
Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Hamilton County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Some Hamilton County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.
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 Indiana'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. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.