Jay County, IN: EPA's radon zone, explained

EPA places Jay County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Rank it against the rest of the country and Jay County lands in the 82nd percentile for radon potential.

Where Jay County sits nationally

Jay County, Indiana is home to about 20,164 people across 383.905 square miles. Averaged across its land area, Jay County runs about 53 people per square mile. By population, Jay County is the 572nd largest of every county sharing its EPA zone — the 46th percentile by population within that zone. Geologically, Jay County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Jay County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. 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 Jay County specifically.

Next steps for a home in Jay County

For a Jay 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 Indiana's state radon program

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

Where Jay County's figures come from

Jay 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.