Tillman County, OK: EPA's radon zone, explained

EPA places Tillman 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. Rank it against the rest of the country and Tillman County lands in the 4th percentile for radon potential.

How Tillman County compares

Tillman County, Oklahoma is home to about 6,736 people across 871.134 square miles. Population density there runs about 8 people per square mile. By population, Tillman County is the 909th largest of every county sharing its EPA zone — the 12th percentile by population within that zone. Tillman County falls in EPA Radon Region 6, one of 503 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Tillman 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. Low doesn't mean zero: EPA's own data shows homes in Zone 3 counties like Tillman County testing above the action level often enough that skipping a test isn't the safe assumption.

Testing and mitigation in Tillman County

For a Tillman County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Oklahoma's state radon program

For Tillman County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Tillman County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

Where Tillman County's figures come from

Tillman 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.