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

EPA places Washington County in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Washington County sits at the 62nd percentile nationally for radon potential — above 62 of every 100 rated counties.

Washington County by the numbers

Washington County, Pennsylvania is home to about 210,434 people across 857.01 square miles. Averaged across its land area, Washington County runs about 246 people per square mile. By population, Washington County is the 116th largest of every county sharing its EPA zone — the 89th percentile by population within that zone. EPA's geology-based Region 3 groups Washington County with 244 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Call it a middle case: above the 1.3 pCi/L most US homes average, below the 4 pCi/L line EPA uses to recommend mitigation — that's Washington County's Zone 2 prediction. A Zone 2 rating is a moderate county-wide average, not a guarantee about any one house in Washington County — testing is the only way to know an individual home's actual level.

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 Pennsylvania'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

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.