Radon Levels in Maryland

24 counties — 8 high risk, 9 moderate, 7 low risk

8
9
7
Zone 1 High (33.3%) Zone 2 Moderate (37.5%) Zone 3 Low (29.2%)

Maryland Radon Zone Map

Counties colored by EPA radon zone. Red = Zone 1, Orange = Zone 2, Green = Zone 3.

Highest-Risk Counties

Baltimore33.5% above action level
Calvert33.3% above action level
Carroll40% above action level
Frederick36.8% above action level
Harford39.5% above action level
Howard21.3% above action level
Montgomery21.2% above action level
Washington50% above action level

Check Your Maryland ZIP Code

All 24 Counties — By Radon Risk

CountyEPA ZoneTests% Above 4 pCi/L
Baltimore High 158 33.5%
Calvert High 18 33.3%
Carroll High 30 40%
Frederick High 38 36.8%
Harford High 43 39.5%
Howard High 47 21.3%
Montgomery High 151 21.2%
Washington High 24 50%
Allegany Moderate 12 50%
Anne Arundel Moderate 95 36.8%
Baltimore Moderate 115 28.7%
Cecil Moderate 16 37.5%
Charles Moderate 25 32%
Garrett Moderate 5 —
Prince George's Moderate 141 24.1%
Somerset Moderate 5 —
St. Mary's Moderate 15 33.3%
Caroline Low 4 —
Dorchester Low 7 57.1%
Kent Low — —
Queen Anne's Low 10 —
Talbot Low 10 40%
Wicomico Low 17 41.2%
Worcester Low 12 50%

Sources: EPA Map of Radon Zones, CDC Environmental Health Tracking Network

Frequently Asked Questions

How many counties in Maryland have high radon risk?

Maryland has 8 counties classified as EPA Zone 1 (high radon risk), 9 as Zone 2 (moderate), and 7 as Zone 3 (low risk).

Is radon a problem in Maryland?

Maryland has 8 high-risk counties where elevated radon is likely. The EPA recommends all homes in Maryland be tested for radon, regardless of which zone they're in.

How do I check radon levels for my Maryland address?

Enter your ZIP code in the search box above to see your county's EPA radon zone and available testing data. For your specific home's radon level, you'll need a radon test kit.