Jersey County, IL: EPA's radon zone, explained

EPA places Jersey 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. That puts Jersey County in the 82nd percentile nationally for radon potential — higher than 82% of the counties EPA has rated.

Where Jersey County sits nationally

Jersey County, Illinois is home to about 21,150 people across 369.556 square miles. Averaged across its land area, Jersey County runs about 57 people per square mile. By population, Jersey County is the 556th largest of every county sharing its EPA zone — the 48th percentile by population within that zone. EPA's geology-based Region 5 groups Jersey County with 523 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Jersey County

Where the national indoor average runs about 1.3 pCi/L, Jersey 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 Jersey County specifically.

Testing and mitigation in Jersey County

For a Jersey 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 Illinois's state radon program

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

Where Jersey County's figures come from

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