What EPA's radon map says about Franklin County

Franklin County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. That puts Franklin County in the 96th percentile nationally for radon potential — higher than 96% of the counties EPA has rated.

How Franklin County compares

About 159,285 people live in Franklin County, Pennsylvania, spread over 772.279 square miles. That works out to roughly 206 people per square mile. Among counties sharing Franklin County's EPA zone, it outranks 88% of them by population. Geologically, Franklin County is grouped into EPA Region 3 alongside 244 other counties that share its rock and soil setting.

Zone vs. an actual test

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Franklin County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. Being in Zone 1 raises the odds Franklin 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 Franklin County tests above the action level

Mitigation cost doesn't depend on Franklin 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 Pennsylvania's state radon program

Franklin County's test kit answers today; a Airthings radon monitor keeps answering for Franklin 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

Franklin County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.