What EPA's radon map says about Frederick County

EPA places Frederick County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Frederick County sits at the 94th percentile nationally for radon potential — above 94 of every 100 rated counties.

Frederick County by the numbers

About 98,109 people live in Frederick County, Virginia, spread over 413.135 square miles. Population density there runs about 237 people per square mile. Among counties sharing Frederick County's EPA zone, it outranks 81% of them by population. EPA's geology-based Region 3 groups Frederick County with 244 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Frederick County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Being in Zone 1 raises the odds Frederick County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

If Frederick County tests above the action level

Mitigation cost doesn't depend on Frederick 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 Virginia's state radon program

Frederick County's test kit answers today; a Airthings radon monitor keeps answering for Frederick County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

More on how this number was built

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