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

Mercer County is mapped as Zone 2 - Moderate Potential by EPA — meaning the county-wide average indoor level is predicted between 2 and 4 pCi/L. Rank it against the rest of the country and Mercer County lands in the 60th percentile for radon potential.

Where Mercer County sits nationally

Mercer County, Pennsylvania is home to about 108,140 people across 672.538 square miles. Averaged across its land area, Mercer County runs about 161 people per square mile. By population, Mercer County is the 186th largest of every county sharing its EPA zone — the 82nd percentile by population within that zone. EPA's geology-based Region 3 groups Mercer County with 244 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

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 Mercer County's Zone 2 prediction. A county-wide moderate average, like Mercer County's, can still hide a specific house well above or below it — testing is what actually answers the question.

If Mercer County tests above the action level

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

Where Mercer 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.