What EPA's radon map says about Union County

EPA's own radon map rates Union County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. Nationally that's the 44th percentile for radon potential — Union County outranks 44% of every county EPA has rated.

Union County by the numbers

About 16,886 people live in Union County, Illinois, spread over 413.412 square miles. Population density there runs about 41 people per square mile. Among counties sharing Union County's EPA zone, it outranks 35% of them by population. Union County falls in EPA Radon Region 5, one of 524 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Union County's predicted average falls between EPA's 4 pCi/L action level and the national indoor average of about 1.3 pCi/L (outdoor air runs roughly 0.4 pCi/L). A Zone 2 rating is a moderate county-wide average, not a guarantee about any one house in Union County — testing is the only way to know an individual home's actual level.

Testing and mitigation in Union County

Mitigation cost doesn't depend on Union 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

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

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.