Pennsylvania Radon Levels
49Zone 1 (High)
17Zone 2 (Moderate)
1Zone 3 (Low)
73% of counties in Pennsylvania are classified as EPA Zone 1 (highest radon potential), meaning predicted average indoor radon levels exceed 4 pCi/L — the EPA action level. The EPA recommends that all homes be tested for radon, regardless of zone classification.
| County | EPA Zone | Risk Level |
|---|---|---|
| Adams County | Zone 1 | Highest Potential |
| Allegheny County | Zone 1 | Highest Potential |
| Armstrong County | Zone 1 | Highest Potential |
| Beaver County | Zone 1 | Highest Potential |
| Bedford County | Zone 1 | Highest Potential |
| Berks County | Zone 1 | Highest Potential |
| Blair County | Zone 1 | Highest Potential |
| Bradford County | Zone 1 | Highest Potential |
| Bucks County | Zone 1 | Highest Potential |
| Butler County | Zone 1 | Highest Potential |
| Cambria County | Zone 2 | Moderate Potential |
| Cameron County | Zone 1 | Highest Potential |
| Carbon County | Zone 1 | Highest Potential |
| Centre County | Zone 1 | Highest Potential |
| Chester County | Zone 1 | Highest Potential |
| Clarion County | Zone 1 | Highest Potential |
| Clearfield County | Zone 1 | Highest Potential |
| Clinton County | Zone 1 | Highest Potential |
| Columbia County | Zone 1 | Highest Potential |
| Crawford County | Zone 2 | Moderate Potential |
| Cumberland County | Zone 1 | Highest Potential |
| Dauphin County | Zone 1 | Highest Potential |
| Delaware County | Zone 1 | Highest Potential |
| Elk County | Zone 2 | Moderate Potential |
| Erie County | Zone 2 | Moderate Potential |
| Fayette County | Zone 2 | Moderate Potential |
| Forest County | Zone 2 | Moderate Potential |
| Franklin County | Zone 1 | Highest Potential |
| Fulton County | Zone 1 | Highest Potential |
| Greene County | Zone 2 | Moderate Potential |
| Huntingdon County | Zone 1 | Highest Potential |
| Indiana County | Zone 1 | Highest Potential |
| Jefferson County | Zone 2 | Moderate Potential |
| Juniata County | Zone 1 | Highest Potential |
| Lackawanna County | Zone 1 | Highest Potential |
| Lancaster County | Zone 1 | Highest Potential |
| Lawrence County | Zone 2 | Moderate Potential |
| Lebanon County | Zone 1 | Highest Potential |
| Lehigh County | Zone 1 | Highest Potential |
| Luzerne County | Zone 1 | Highest Potential |
| Lycoming County | Zone 1 | Highest Potential |
| McKean County | Zone 2 | Moderate Potential |
| Mercer County | Zone 2 | Moderate Potential |
| Mifflin County | Zone 1 | Highest Potential |
| Monroe County | Zone 1 | Highest Potential |
| Montgomery County | Zone 1 | Highest Potential |
| Montour County | Zone 1 | Highest Potential |
| Northampton County | Zone 1 | Highest Potential |
| Northumberland County | Zone 1 | Highest Potential |
| Perry County | Zone 1 | Highest Potential |
| Philadelphia County | Zone 3 | Lowest Potential |
| Pike County | Zone 2 | Moderate Potential |
| Potter County | Zone 2 | Moderate Potential |
| Schuylkill County | Zone 1 | Highest Potential |
| Snyder County | Zone 1 | Highest Potential |
| Somerset County | Zone 2 | Moderate Potential |
| Sullivan County | Zone 1 | Highest Potential |
| Susquehanna County | Zone 1 | Highest Potential |
| Tioga County | Zone 1 | Highest Potential |
| Union County | Zone 1 | Highest Potential |
| Venango County | Zone 1 | Highest Potential |
| Warren County | Zone 2 | Moderate Potential |
| Washington County | Zone 2 | Moderate Potential |
| Wayne County | Zone 2 | Moderate Potential |
| Westmoreland County | Zone 1 | Highest Potential |
| Wyoming County | Zone 1 | Highest Potential |
| York County | Zone 1 | Highest Potential |