Radon levels in Maryland: Low
The model predicts a population-weighted basement average of 1.3 pCi/L across Maryland's 24 counties - about 28% below the US average of 1.8 pCi/L. Above-ground floors average 1.0 pCi/L.
Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.
8 / 24
EPA Zone 1 counties (33%)
9 / 7
Zone 2 / Zone 3 counties
0
counties predicted ≥ 4 pCi/L
0%
of ZIP codes predicted ≥ 4 pCi/L
Maryland counties by predicted radon
Sorted highest to lowest predicted basement average. 24 counties.
| County | Predicted basement | Upstairs | Grade | EPA zone | ZIPs |
|---|---|---|---|---|---|
| Washington County | 2.9 pCi/L | 2.1 | Moderate | EPA Zone 1 | 14 |
| Allegany County | 2.6 pCi/L | 1.6 | Moderate | EPA Zone 2 | 8 |
| Garrett County | 2.5 pCi/L | 1.3 | Moderate | EPA Zone 2 | 11 |
| Carroll County | 1.8 pCi/L | 1.6 | Low | EPA Zone 1 | 9 |
| Calvert County | 1.6 pCi/L | 1.3 | Low | EPA Zone 1 | 12 |
| Cecil County | 1.5 pCi/L | 1.1 | Low | EPA Zone 2 | 13 |
| Frederick County | 1.5 pCi/L | 1.3 | Low | EPA Zone 1 | 24 |
| Caroline County | 1.4 pCi/L | 0.7 | Low | EPA Zone 3 | 7 |
| Kent County | 1.4 pCi/L | 0.8 | Low | EPA Zone 3 | 9 |
| St. Mary's County | 1.4 pCi/L | 1.0 | Low | EPA Zone 2 | 22 |
| Talbot County | 1.4 pCi/L | 0.8 | Low | EPA Zone 3 | 13 |
| Queen Anne's County | 1.4 pCi/L | 0.7 | Low | EPA Zone 3 | 12 |
| Charles County | 1.4 pCi/L | 0.9 | Low | EPA Zone 2 | 21 |
| Worcester County | 1.4 pCi/L | 0.6 | Low | EPA Zone 3 | 9 |
| Dorchester County | 1.4 pCi/L | 0.7 | Low | EPA Zone 3 | 14 |
| Somerset County | 1.4 pCi/L | 0.7 | Low | EPA Zone 2 | 6 |
| Wicomico County | 1.3 pCi/L | 0.6 | Low | EPA Zone 3 | 15 |
| Harford County | 1.3 pCi/L | 1.0 | Low | EPA Zone 1 | 18 |
| Howard County | 1.2 pCi/L | 1.0 | Low | EPA Zone 1 | 19 |
| Prince George's County | 1.2 pCi/L | 0.9 | Low | EPA Zone 2 | 34 |
| Anne Arundel County | 1.2 pCi/L | 0.9 | Low | EPA Zone 2 | 35 |
| Montgomery County | 1.2 pCi/L | 0.9 | Low | EPA Zone 1 | 42 |
| Baltimore County | 1.1 pCi/L | 0.9 | Low | EPA Zone 1 | 37 |
| Baltimore city | 1.0 pCi/L | 0.8 | Low | EPA Zone 2 | 20 |
Maryland radon questions
- Is radon high in Maryland?
- Maryland's population-weighted predicted basement average is 1.3 pCi/L, about 28% below the US average of 1.8. 0 of its 24 modeled counties are predicted at or above the EPA action level of 4 pCi/L, 3 are in the 2-4 "consider fixing" range and 21 are below 2. 0% of Maryland ZIP codes are predicted at 4 or higher.
- Which Maryland county has the highest radon?
- Washington County has the highest predicted basement average in Maryland at 2.9 pCi/L (EPA Zone 1). The lowest is Baltimore city at 1.0 pCi/L. These are modeled area averages; individual homes in any county can test far higher.
- How many EPA Zone 1 counties are in Maryland?
- 8 of Maryland's 24 counties (33%) are EPA Zone 1 (highest potential), 9 are Zone 2 and 7 are Zone 3. The EPA zone map dates from 1993; the predicted values on this page come from a 2001-2021 model built on millions of actual tests, so the two can disagree for a given county.
- Should I test for radon in Maryland?
- Yes. Even though Maryland's predicted average is below 2 pCi/L, the EPA recommends every home be tested - radon varies house to house, and 10.1% of Maryland ZIP codes are still predicted at 2 pCi/L or higher.
Maryland radon program
Many states offer free or discounted test kits and keep lists of certified mitigators. Find the Maryland radon office through the EPA state radon contacts page. Then read how to test and what mitigation costs.