What EPA's radon map says about Ogle County

Ogle County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Ogle County sits at the 90th percentile nationally for radon potential — above 90 of every 100 rated counties.

How Ogle County compares

About 51,345 people live in Ogle County, Illinois, spread over 758.654 square miles. Averaged across its land area, Ogle County runs about 68 people per square mile. Among counties sharing Ogle County's EPA zone, it outranks 71% of them by population. Geologically, Ogle 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 Ogle County

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Ogle County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Being in Zone 1 raises the odds Ogle County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

Next steps for a home in Ogle County

Mitigation cost doesn't depend on Ogle County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Illinois's state radon program

Ogle County's test kit answers today; a Airthings radon monitor keeps answering for Ogle County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

More on how this number was built

Ogle 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.