Locations and reports
Radon Levels in Maryland
What this means for you
- Your area: EPA rates 8 of Maryland's 24 classified counties Zone 1, the highest of its three radon zones. Zones are predictions for whole counties, and homes with elevated levels occur in all three zones.
- Local tests: CDC publishes Maryland's radon test results by county. Open your county below to see its figures.
- Your home: The only way to know your home’s level is to test it.
pCi/L (picocuries per liter) is the unit radon is measured in. EPA recommends fixing a home at 4 pCi/L or above, its action level.
For Maryland, EPA's Map of Radon Zones places 8 of its 24 classified counties in Zone 1, highest predicted potential, a prediction for each county as a whole. Radon levels vary from home to home, so only a test measures the level in yours.
Predicted: EPA radon zone
24 of 24 counties classified
EPA classifies counties, not states. Of the 24 counties in Maryland with a zone, 8 are in Zone 1, 9 in Zone 2 and 7 in Zone 3.
- Zone 1: Highest predicted potentialgreater than 4 pCi/L8 of 24 counties · 33.3%
- Zone 2: Moderate predicted potential2 to 4 pCi/L9 of 24 counties · 37.5%
- Zone 3: Lower predicted potentialless than 2 pCi/L7 of 24 counties · 29.2%
An EPA radon zone describes predicted potential across a whole county. It is not intended to determine whether any individual home should be tested, and homes with elevated levels occur in all three zones. EPA recommends testing every home regardless of zone, and testing is the only way to know the radon level in a specific building.
This is a county-level geologic prediction. It is not a measurement of any address, and houses with elevated radon are found in all three zones.
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
CDC publishes Maryland's radon test figures by county: 24 of its 24 counties have one. Each county's share is in the county list.
Maryland, In figures
Maryland in figures
What the published data says about Maryland, in words. A zone and a share of tests describe an area, never the level in any one home.
Predicted
PredictedEPA places 8 of Maryland's 24 counties in Zone 1, 9 in Zone 2 and 7 in Zone 3.
Zone 1 counties, A to Z, begin with Baltimore County, Calvert County and Carroll County; the county section below lists all 8.
Compared
Calculated by Radon41133% of Maryland's counties with a zone on file are in Zone 1, a smaller share than across all U.S. counties (34%). It is a share of counties, not of land, people or homes.
Reported tests
MeasuredCDC has no statewide testing figure for Maryland on file here.
24 of the 24 counties have a published county figure; the most tests in each one's latest year were reported for Montgomery County (6,980 in 2017), Baltimore County (6,118 in 2017) and Harford County (4,534 in 2017).
Maryland's radon program and its page are under Local resources.
Maryland, Counties
Maryland counties by EPA zone
PredictedAll 24 counties, by the zone EPA predicts for each. Every county has its own report.
Zone 1: highest predicted potential8
- Baltimore County19.1% of reported tests at or above 4 pCi/L, 2017
- Calvert County30.2% of reported tests at or above 4 pCi/L, 2017
- Carroll County41.9% of reported tests at or above 4 pCi/L, 2017
- Frederick County28.1% of reported tests at or above 4 pCi/L, 2017
- Harford County22.6% of reported tests at or above 4 pCi/L, 2017
- Howard County30.8% of reported tests at or above 4 pCi/L, 2017
- Montgomery County18.0% of reported tests at or above 4 pCi/L, 2017
- Washington County56.0% of reported tests at or above 4 pCi/L, 2017
Zone 2: moderate predicted potential9
- Allegany County35.7% of reported tests at or above 4 pCi/L, 2017
- Anne Arundel County17.4% of reported tests at or above 4 pCi/L, 2017
- Baltimore city7.9% of reported tests at or above 4 pCi/L, 2017
- Cecil County24.9% of reported tests at or above 4 pCi/L, 2017
- Charles County24.1% of reported tests at or above 4 pCi/L, 2017
- Garrett County37.4% of reported tests at or above 4 pCi/L, 2017
- Prince George's County19.0% of reported tests at or above 4 pCi/L, 2017
- Somerset County0.0% of reported tests at or above 4 pCi/L, 2017
- St. Mary's County20.9% of reported tests at or above 4 pCi/L, 2017
Zone 3: lower predicted potential7
- Caroline County0.0% of reported tests at or above 4 pCi/L, 2017
- Dorchester County16.7% of reported tests at or above 4 pCi/L, 2017
- Kent County52.6% of reported tests at or above 4 pCi/L, 2017
- Queen Anne's County16.9% of reported tests at or above 4 pCi/L, 2017
- Talbot County7.7% of reported tests at or above 4 pCi/L, 2017
- Wicomico County0.0% of reported tests at or above 4 pCi/L, 2017
- Worcester County0.0% of reported tests at or above 4 pCi/L, 2017
Maryland, Local resources
Local resources in Maryland
Who to ask in Maryland: the state's radon program, test kits and professionals.
Maryland's radon program
Maryland Department of Health
Maryland’s radon program answers questions about testing, mitigation and the rules where you live.
- Phone
- 1-866-703-3266
Test kits
The program says: Maryland residents may be eligible for a free radon test kit.
Radon professionals
5 professionals are listed in Maryland.
Professionals in MarylandMaryland, Questions
Questions about radon in Maryland
Common questions9 questions, answered from the figures above
Is radon a problem in Maryland?
EPA's Map of Radon Zones places 8 of the 24 Maryland counties it classifies in Zone 1, the highest predicted potential, 9 in Zone 2 and 7 in Zone 3. An EPA radon zone describes predicted potential across a whole county. It is not intended to determine whether any individual home should be tested, and homes with elevated levels occur in all three zones. EPA recommends testing every home regardless of zone, and testing is the only way to know the radon level in a specific building.
How do I get a radon test in Maryland?
EPA says you can test your home yourself or hire a qualified radon test company, and that either approach takes only a small amount of time and effort. The Maryland radon program is the place to ask about certified testers and any test kit offer it runs.
How to test a homeFree and low-cost kits by stateMaryland radon program
Who does radon mitigation in Maryland?
Radon411's Maryland directory lists 5 certified radon companies. EPA recommends having a qualified contractor fix a home with a radon problem, because lowering high radon levels takes technical knowledge and special skills, and some states require the work to be done by a licensed or certified professional.
How radon mitigation worksWhat mitigation costsRadon professionals in Maryland
Which Maryland counties are in EPA radon Zone 1?
8 counties are in Zone 1: Baltimore County, Calvert County, Carroll County, Frederick County, Harford County, Howard County, Montgomery County, Washington County. Zone 1 is EPA's class for highest predicted potential, a predicted average indoor screening level greater than 4 pCi/L. A zone is a prediction for a county, not a measurement of any home.
Radon in Baltimore CountyRadon in Calvert CountyRadon in Carroll County
Which Maryland counties have the highest radon?
24 of Maryland's 24 counties have an EPA radon zone published here. Radon411 will not rank counties on data it does not hold, and a zone is a prediction for an area rather than a measurement of any building.
What share of radon tests in Maryland are high?
CDC has published no statewide radon testing statistics for Maryland, so we cannot give a figure. Where CDC does publish one, the percentage describes radon tests reported to CDC, not homes.
Which EPA region is Maryland in?
Maryland is in EPA Region 3: Mid-Atlantic.
Do I need to test my home in Maryland?
Yes, wherever you live in the state. Testing is the only way to know the radon level in a specific building. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L.
Why does this page show coverage rather than one radon level for Maryland?
A statewide figure averages counties with very different geology and very different numbers of reported tests, so it hides more than it shows. The county report is the level at which the EPA zone, the geologic potential and the reported testing statistics are actually published, which is why the county table above links to every one of them.
What these figures mean if you own, buy, sell or rent
The zone counts on this page describe counties across Maryland. They are predictions for areas, and none of them measures your building.
- How to test a home
If you own your home
Test the lowest lived-in level; a short-term kit screens in days, a long-term kit reflects the year.
- Buying a house: radon guide
If you are buying
Ask for past results and any system's post-mitigation test, and test during the sale.
- Selling a house: radon guide
If you are selling
Testing before you list puts the timing in your hands; disclosure rules differ by state.
- Radon in rental homes
If you rent, or rent out a home
A tenant can test; a fix is the owner's to make, and duties differ by state.
How long a test has to run, under what conditions, and what EPA says a result means: the testing standard, in full.
Maryland, Products
Testing and mitigation products
Whatever the figures for Maryland show, only a test tells you about one home.
Testing
- Short-term test kitsPassive detectors exposed for a few days under closed-building conditions, then analyzed by a lab.
- Long-term test kitsDetectors exposed for more than 90 days, for a closer picture of the annual average.
- Continuous monitorsPowered devices that log radon on a repeating cycle, often used for transaction tests.
- Digital detectorsConsumer devices that display a running radon reading without a lab.
- Water radon testsKits for radon dissolved in well water, analyzed by a lab.
Mitigation
- Mitigation fansThe inline fan that keeps a soil depressurization system running, sized by the installer.
- System indicatorsU-tube manometers and fan alarms that show whether a mitigation system is still working.
- Sealing materialsCrack, joint and sump sealing used alongside a mitigation system, not instead of one.
Maryland / Next steps
What to do next
Learn
Know what radon is
What radon is, how it gets indoors, and why a county zone is not a reading for your home.
Learn about radonTest
Test the building you live in
Short-term or long-term, where the device goes, and closed-house conditions.
How to testFix
Bring a high level down
How a mitigation system works, and the retest that confirms it.
How mitigation worksFind a pro
Hire a certified professional
Measurement and mitigation professionals by state, with their certifications.
Find a professional
Informational. Follow EPA guidance. EPA says all radon tests should be taken for a minimum of 48 hours, with windows and doors closed from 12 hours before a short-term test.