Is Richland County, IL a radon risk area?

EPA places Richland County in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Nationally that's the 43rd percentile for radon potential — Richland County outranks 43% of every county EPA has rated.

How Richland County compares

About 15,362 people live in Richland County, Illinois, spread over 360.047 square miles. That works out to roughly 43 people per square mile. Rank 708 by population within its EPA zone puts Richland County at the 31st percentile among zone peers. Richland County falls in EPA Radon Region 5, one of 524 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Call it a middle case: above the 1.3 pCi/L most US homes average, below the 4 pCi/L line EPA uses to recommend mitigation — that's Richland County's Zone 2 prediction. Richland County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

If Richland County tests above the action level

Nothing about Richland County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Illinois's state radon program

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

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.