Maryland Radon Levels
8Zone 1 (High)
9Zone 2 (Moderate)
7Zone 3 (Low)
33% of counties in Maryland 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 |
|---|---|---|
| Allegany County | Zone 2 | Moderate Potential |
| Anne Arundel County | Zone 2 | Moderate Potential |
| Baltimore County | Zone 1 | Highest Potential |
| Calvert County | Zone 1 | Highest Potential |
| Caroline County | Zone 3 | Lowest Potential |
| Carroll County | Zone 1 | Highest Potential |
| Cecil County | Zone 2 | Moderate Potential |
| Charles County | Zone 2 | Moderate Potential |
| Dorchester County | Zone 3 | Lowest Potential |
| Frederick County | Zone 1 | Highest Potential |
| Garrett County | Zone 2 | Moderate Potential |
| Harford County | Zone 1 | Highest Potential |
| Howard County | Zone 1 | Highest Potential |
| Kent County | Zone 3 | Lowest Potential |
| Montgomery County | Zone 1 | Highest Potential |
| Prince George's County | Zone 2 | Moderate Potential |
| Queen Anne's County | Zone 3 | Lowest Potential |
| St. Mary's County | Zone 2 | Moderate Potential |
| Somerset County | Zone 2 | Moderate Potential |
| Talbot County | Zone 3 | Lowest Potential |
| Washington County | Zone 1 | Highest Potential |
| Wicomico County | Zone 3 | Lowest Potential |
| Worcester County | Zone 3 | Lowest Potential |
| Baltimore city | Zone 2 | Moderate Potential |