What EPA's radon map says about Coryell County

EPA places Coryell County in Zone 3 - Low Potential — a predicted county-wide average indoor radon level below 2 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. That puts Coryell County in the 25th percentile nationally for radon potential — higher than 25% of the counties EPA has rated.

How Coryell County compares

About 86,370 people live in Coryell County, Texas, spread over 1,052.247 square miles. That works out to roughly 82 people per square mile. Among counties sharing Coryell County's EPA zone, it outranks 77% of them by population. Geologically, Coryell County is grouped into EPA Region 6 alongside 502 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

Coryell County's predicted average sits below the national indoor average of about 1.3 pCi/L, well under EPA's 4 pCi/L action level. Don't read Zone 3 as a pass for Coryell County — EPA's guidance to test every home makes no exception for counties predicted low.

If Coryell County tests above the action level

Mitigation cost doesn't depend on Coryell 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 Texas's state radon program

Coryell County's test kit answers today; a Airthings radon monitor keeps answering for Coryell 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. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.