Loudoun County, VA: EPA's radon zone, explained

EPA places Loudoun 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. Loudoun County sits at the 64th percentile nationally for radon potential — above 64 of every 100 rated counties.

How Loudoun County compares

Loudoun County, Virginia is home to about 443,380 people across 515.746 square miles. Population density there runs about 860 people per square mile. By population, Loudoun County is the 56th largest of every county sharing its EPA zone — the 95th percentile by population within that zone. Geologically, Loudoun County is grouped into EPA Region 3 alongside 244 other counties that share its rock and soil setting.

What this actually means for a house in Loudoun County

Loudoun County's predicted average falls between EPA's 4 pCi/L action level and the national indoor average of about 1.3 pCi/L (outdoor air runs roughly 0.4 pCi/L). A county-wide moderate average, like Loudoun County's, can still hide a specific house well above or below it — testing is what actually answers the question.

If Loudoun County tests above the action level

For a Loudoun 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 Virginia's state radon program

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

Where Loudoun County's figures come from

Loudoun County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Loudoun County carries, the zone explainer covers what it does and doesn't tell you about any one house.