Maryland Radon Map, Levels & Testing Guide
Browse the 12 listed county pages surfaced for Maryland. Open a listed county to compare its EPA zone, source caveats, testing meaning, and when mitigation pricing becomes worth checking.
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Official Evidence in Maryland
12 of 12 listed counties have official evidence
Open a county page to see the processed verdict: source confidence, local burden, state percentile, and the next step for no reading, 2.0-3.9, or 4.0+ pCi/L.
100%
covered
Measured
12
State source
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CDC source
12
Needs source detail
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Measured Risk Leaders in Maryland
County rankings from actual reported radon tests
These lists rank the visible Maryland county pages by measured radon signals, not by the EPA zone label alone. Use them to spot where the state hub has a real data story before opening individual county pages.
12
measured counties
State-level verdict
This hub has measured high-burden counties, so the first click should be evidence-led.
The state hub is now doing a decision job: it separates first-click counties, retest counties, and lower-signal counties from 12 visible county measurement rows. 5 counties cross the high measured-burden band, so those pages should answer testing and 4.0+ action questions most directly.
First-click counties
Open Washington County first when you need the strongest local answer. It is tagged Test-now from 56.0% 4.0+ - 10.1 pCi/L primary - 988 tests. 7 visible measured counties are elevated or high enough to review before lower-signal counties.
Buyer/seller lane
Buyer/seller lane: start with the elevated or high counties, require a fresh lowest-level test, and turn any 4.0+ property result into quote or credit math. The hub has 12 CDC-backed county rows to support that routing.
Retest lane
Retest lane: 2.0-3.9 pCi/L deserves more caution in the elevated/high county set than in lower-signal counties. The hub should send those users to county pages before product or cost paths.
Best county pages to open first
Start with these local evidence pages
Ranked by measured burden, 4.0+ share, test volume, and whether the EPA zone understates the measurement signal.
Washington County
CDC Tracking
56.0% 4.0+ - 10.1 pCi/L primary - 988 tests
Washington County is a first-click page: 56.0% of reported tests at or above 4.0 and 10.1 pCi/L primary result. Route no-reading users to a test now and 4.0+ users to quote or credit planning.
Carroll County
CDC Tracking
41.9% 4.0+ - 8.2 pCi/L primary - 2,602 tests
Carroll County is a first-click page: 41.9% of reported tests at or above 4.0 and 8.2 pCi/L primary result. Route no-reading users to a test now and 4.0+ users to quote or credit planning.
Frederick County
CDC Tracking
28.1% 4.0+ - 5.2 pCi/L primary - 2,947 tests
Frederick County is a first-click page: 28.1% of reported tests at or above 4.0 and 5.2 pCi/L primary result. Route no-reading users to a test now and 4.0+ users to quote or credit planning.
Howard County
CDC Tracking
30.8% 4.0+ - 4.3 pCi/L primary - 3,429 tests
Howard County is a first-click page: 30.8% of reported tests at or above 4.0 and 4.3 pCi/L primary result. Route no-reading users to a test now and 4.0+ users to quote or credit planning.
Highest 4.0+ share
Primary result 10.1 pCi/L - high-end 413.3 pCi/L
CDC Tracking
Primary result 8.2 pCi/L - high-end 355.4 pCi/L
CDC Tracking
Primary result 4.3 pCi/L - high-end 172.3 pCi/L
CDC Tracking
Primary result 4.1 pCi/L - high-end 83.7 pCi/L
CDC Tracking
Primary result 5.2 pCi/L - high-end 193.9 pCi/L
CDC Tracking
Highest high-end reading
4.0+ share 18.0% - primary result 2.7 pCi/L
CDC Tracking
4.0+ share 56.0% - primary result 10.1 pCi/L
CDC Tracking
4.0+ share 41.9% - primary result 8.2 pCi/L
CDC Tracking
4.0+ share 17.4% - primary result 2.9 pCi/L
CDC Tracking
4.0+ share 19.1% - primary result 2.9 pCi/L
CDC Tracking
Most reported tests
4.0+ share 18.0% - primary result 2.7 pCi/L
CDC Tracking
4.0+ share 19.1% - primary result 2.9 pCi/L
CDC Tracking
4.0+ share 22.6% - primary result 3.4 pCi/L
CDC Tracking
4.0+ share 30.8% - primary result 4.3 pCi/L
CDC Tracking
4.0+ share 28.1% - primary result 5.2 pCi/L
CDC Tracking
Measured pattern
Among 12 visible counties with measurement tables, 5 land in the high measured-burden band and 7 land in high or elevated measured-burden bands. That lets this hub rank counties by observed test distribution instead of repeating the EPA map.
Map vs measurements
1 elevated measured counties are not EPA Zone 1. Those are the pages where the actual test distribution matters more than a map-only answer.
Source confidence
The measured rows shown here use CDC Tracking. This is still official evidence, but the hub should keep source caveats visible until a stable state table is available.
Already Tested
View Maryland Cost Estimates
If you already have a radon result, skip the directory and move straight to local price guidance.
Understand the Number
2.0 vs 4.0 vs 8.0 pCi/L
Use the parent levels guide if you need the plain-English meaning of a radon result before browsing counties.
Need a Number First
Read the Testing Guide
Use the fastest valid radon test setup before you compare quotes or ask whether mitigation is worth it.
Browse Counties
Jump to the Directory
Open your county to see its EPA zone, testing meaning, and the point where mitigation becomes worth pricing.
Official State Resource
Maryland radon program and rules
Use the state program link to verify local radon guidance, disclosure language, and contractor credential expectations before you act on an estimate.
Disclosure rule tracked
Maryland requires sellers to disclose environmental hazards including radon through the Residential Property Disclosure and Disclaimer Statement.
Credential note
Maryland does not require specific radon licensing but recommends NRPP or AARST-certified professionals.
Already tested? Get your itemized mitigation cost estimate.
View Maryland Mitigation Cost Estimates ->