Chester County, PA radon potential

EPA places Chester 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. Chester County sits at the 99th percentile nationally for radon potential — above 99 of every 100 rated counties.

Where Chester County sits nationally

Chester County, Pennsylvania is home to about 560,745 people across 750.553 square miles. Averaged across its land area, Chester County runs about 747 people per square mile. Within its own EPA zone, Chester County is bigger by population than 97% of the counties that share it. Chester County falls in EPA Radon Region 3, one of 245 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Chester County carries a Zone 1 label because its predicted average clears 4 pCi/L outright — three-plus times the 0.4 pCi/L typical outdoors and above the 1.3 pCi/L most homes see. Some Chester County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

Testing and mitigation in Chester County

A short-term test kit is the standard first step and typically costs far less than mitigation itself. If a test comes back at or above 4 pCi/L, a radon mitigation system for a typical home runs roughly $800–$2,500 (around $1,200 for a common single-family install), driven mainly by foundation type, not by county.

Find Pennsylvania's state radon program

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

Where Chester 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. Whatever zone Chester County carries, the zone explainer covers what it does and doesn't tell you about any one house.