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

EPA places Butler 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. Nationally, Butler County ranks higher in radon potential than 97% of rated counties (the 97th percentile).

Butler County by the numbers

Butler County, Pennsylvania is home to about 199,341 people across 789.482 square miles. Averaged across its land area, Butler County runs about 252 people per square mile. By population, Butler County is the 98th largest of every county sharing its EPA zone — the 91st percentile by population within that zone. Butler County falls in EPA Radon Region 3, one of 245 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Butler County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. Being in Zone 1 raises the odds Butler 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.

Next steps for a home in Butler County

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

Where Butler County's figures come from

Butler 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.