Washington County, NC: EPA's radon zone, explained

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. Nationally that's the 7th percentile for radon potential — Washington County outranks 7% of every county EPA has rated.

Where Washington County sits nationally

Washington County, North Carolina is home to about 10,654 people across 346.51 square miles. Population density there runs about 31 people per square mile. By population, Washington County is the 808th largest of every county sharing its EPA zone — the 22nd percentile by population within that zone. Washington County falls in EPA Radon Region 4, one of 736 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

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.

Next steps for a home in Washington County

For a Washington 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 North Carolina's state radon program

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

Where Washington County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Washington County's numbers. Whatever zone Washington County carries, the zone explainer covers what it does and doesn't tell you about any one house.