Radon zones in Maryland
Last updated
EPA’s Map of Radon Zones places 24 Maryland counties in its three radon potential zones: 8 in Zone 1 (highest), 9 in Zone 2 (moderate), and 7 in Zone 3 (low).
What this means for Maryland homes
Most Maryland counties fall in Zone 2. EPA predicts moderate average indoor levels (2 to 4 pCi/L) across much of Maryland. Many homes will be below the action level, but many will not, and only a test can tell which.
EPA’s guidance is the same everywhere: test your home, fix it if the level is 4 pCi/L or higher, and consider fixing between 2 and 4 pCi/L. The zone map is from 1993 and should not be used to decide whether a single home needs testing.
Maryland radon program
EPA lists the following state contact for Maryland: the state radon program, phone 410-537-3193. Website: health.maryland.gov/phpa/OEHFP/EH/pages/radon.aspx. State programs can tell you about local testing data, free or discounted test kits, disclosure rules for home sales, and credentialed radon professionals.
Maryland counties and their EPA radon zones
| County | EPA radon zone |
|---|---|
| Allegany County | Zone 2 |
| Anne Arundel County | Zone 2 |
| Baltimore city | Zone 2 |
| Baltimore County | Zone 1 |
| Calvert County | Zone 1 |
| Caroline County | Zone 3 |
| Carroll County | Zone 1 |
| Cecil County | Zone 2 |
| Charles County | Zone 2 |
| Dorchester County | Zone 3 |
| Frederick County | Zone 1 |
| Garrett County | Zone 2 |
| Harford County | Zone 1 |
| Howard County | Zone 1 |
| Kent County | Zone 3 |
| Montgomery County | Zone 1 |
| Prince George's County | Zone 2 |
| Queen Anne's County | Zone 3 |
| Somerset County | Zone 2 |
| St. Mary's County | Zone 2 |
| Talbot County | Zone 3 |
| Washington County | Zone 1 |
| Wicomico County | Zone 3 |
| Worcester County | Zone 3 |
County names follow the 2020 Census. Zones from the EPA Map of Radon Zones (text version). Rows marked “zone of” use the zone EPA gave the predecessor or surrounding county.
Next steps: read how to test your home, check a result with the level calculator, or look up a single address by ZIP code.