What EPA's radon map says about Washington County

EPA places Washington 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. Washington County sits at the 23rd percentile nationally for radon potential — above 23 of every 100 rated counties.

How Washington County compares

About 54,060 people live in Washington County, Oklahoma, spread over 415.524 square miles. Averaged across its land area, Washington County runs about 130 people per square mile. Among counties sharing Washington County's EPA zone, it outranks 69% of them by population. Geologically, Washington County is grouped into EPA Region 6 alongside 502 other counties that share its rock and soil setting.

What this actually means for a house in Washington County

At Zone 3, Washington County's predicted county average is under the national indoor average (~1.3 pCi/L) and well below EPA's 4 pCi/L action level — outdoor air nationally runs about 0.4 pCi/L for comparison. A Zone 3 label describes Washington County's average, not any one basement or slab in it — testing is still the only way an individual homeowner actually finds out.

If Washington County tests above the action level

Mitigation cost doesn't depend on Washington 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 Oklahoma's state radon program

Washington County's test kit answers today; a Airthings radon monitor keeps answering for Washington County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 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. Whatever zone Washington County carries, the zone explainer covers what it does and doesn't tell you about any one house.