What EPA's radon map says about Karnes County

EPA's own radon map rates Karnes County zone 3 - low potential, predicting a county-wide average indoor level below 2 pCi/L. Rank it against the rest of the country and Karnes County lands in the 10th percentile for radon potential.

Where Karnes County sits nationally

About 15,137 people live in Karnes County, Texas, spread over 747.752 square miles. Averaged across its land area, Karnes County runs about 20 people per square mile. Among counties sharing Karnes County's EPA zone, it outranks 31% of them by population. Geologically, Karnes County is grouped into EPA Region 6 alongside 502 other counties that share its rock and soil setting.

Zone vs. an actual test

Karnes 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 Karnes County — EPA's guidance to test every home makes no exception for counties predicted low.

If Karnes County tests above the action level

Mitigation cost doesn't depend on Karnes 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

Karnes County's test kit answers today; a Airthings radon monitor keeps answering for Karnes 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

The methodology guide shows exactly which EPA and Census sources feed Karnes County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.