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Maryland Radon Map and Levels by County

Maryland's counties span all three EPA radon zones. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

Predicted
8 of 24counties in Zone 1, EPA's highest radon zone
Measured
By countyCDC publishes Maryland's test figures by county: 24 of 24 counties have one.
Your home
Test to knowNo area figure here is a reading of your home.
How to test this homeFind a certified tester

The data

Maryland, At a glance

Maryland at a glance

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.

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

CDC test figures, county by county

CDC publishes Maryland's radon test figures by county: 24 of its 24 counties have one. Each one's share is in the county list.

Maryland, Counties

Maryland counties by EPA zone

Predicted

Maryland's radon map, then all 24 counties by the zone EPA predicts for each, highest reported share of tests at or above 4 pCi/L first. Each has its own report.

Maryland radon map by county: EPA radon zones. Map of Maryland's 24 counties shaded by EPA radon zone: Zone 1 in red-orange, Zone 2 in amber, Zone 3 in pale sand. 8 in Zone 1, 9 in Zone 2, 7 in Zone 3.
Maryland radon map by countyEPA radon zones for Maryland's counties: 8 counties in Zone 1, 9 counties in Zone 2, 7 counties in Zone 3.Predicted potential for each county, not a reading of any home. Homes with elevated levels of radon have been found in all three zones.

Zone 1: highest predicted potential8

Local help

Maryland, Local resources

Local resources in Maryland

Who to ask in Maryland: its radon program, test kits and professionals.

What Maryland's program says
Phone
1-866-703-3266

Radon Action Brief

National Radon Action MonthPre-sale

The radon brief for your Maryland county, in one dated file.

  • Your area's radon record, explained.
  • Your plan to test this week.
  • Fix costs and pros near you.

Save 64%Sale price: $8.99Price after the sale: $25Ends Jan 31Then $25

Get your Maryland county's BriefSee a free sample

Area data, not a test of the building.

What it means

Maryland, Questions

Questions about radon in Maryland

Common questions

9 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.

Maryland on the radon mapRadon levels by state

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 radon businesses for testing, mitigation or both, each with the licensing list it was read from. 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.

If you own, buy, sell or rent

What these figures mean for each reader, with the guide that covers it

The zone counts on this page describe counties across Maryland. They are predictions for areas, and none of them measures your building.

Maryland in figures

The figures above, said in words

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

      Predicted

      EPA 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 Radon411

      33% 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

    Measured

    CDC 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 (10,969 tests over 2008 to 2017, laboratory), Baltimore County (7,706 tests over 2008 to 2017, laboratory) and Harford County (5,283 tests over 2008 to 2017, laboratory).

Maryland's radon program and its page are under Local resources.

Products

Maryland, Products

Testing and mitigation products

Whatever the figures for Maryland show, only a test tells you about one home.

Test kits and monitors42

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Best radon monitors for Maryland homes, compared

Testing

5

Mitigation

3

Explore

Maryland, Next steps

What to do next

  1. LearnKnow what radon isWhat radon is, how it gets indoors, and why a county zone is not a reading for your home.Learn about radon
  2. TestTest the building you live inShort-term or long-term, where the device goes, and closed-house conditions.How to test
  3. FixBring a high level downHow a mitigation system works, and the retest that confirms it.How mitigation works
  4. Find a proHire a certified professionalMeasurement 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.