Radon · Maryland
Radon in Maryland
Of the 5 Maryland ZIPs zipradar carries, 2 sit in EPA Radon Zone 1 (highest predicted potential, above 4 pCi/L), 3 in Zone 2 (moderate, 2–4 pCi/L). The zone is a county-level EPA prediction, not a reading from any building — it narrows the question but does not settle it, and EPA's own guidance is that the only way to know a specific home is an at-home test kit.
Last verified 2026-09-24 · methodology
Radon by ZIP code in Maryland
EPA's county radon zone for each ZIP zipradar covers. Tap a ZIP for what the zone means and how to test.
| ZIP | EPA radon zone |
|---|---|
| 21201BaltimoreBaltimore (city) | Zone 2 · moderate |
| 20850RockvilleMontgomery County | Zone 1 · highest |
| 21401AnnapolisAnne Arundel County | Zone 2 · moderate |
| 21202BaltimoreBaltimore City | Zone 2 · moderate |
| 20815Chevy ChaseMontgomery County | Zone 1 · highest |
County-level figures from EPA Radon Zones, joined to each ZIP by county. None of them is a measurement at a specific address.
What lands here
Pages show the county zone, what the classification means for home testing recommendations, and state-level supplementary data where available.
Source & refresh
EPA Radon Zones. Refreshed static 1993 baseline plus state-level supplementary updates. Primary source →
Maryland top concern
Chesapeake flood, lead pipes
Maryland has dense FEMA NFHL coverage along Chesapeake Bay tributaries. Baltimore City has extensive LCRR lead-service-line obligations and flagged EPA SDWIS compliance history. Radon Zone 1-2 across most counties.
See Maryland state page for the full state-level rollup across all 12 dimensions.
Read more on radon
Editorial deep-dives explaining the source data, its limits, and how to read it.
EPA Radon Zones — what 1, 2, and 3 mean and when you should test
EPA classifies every US county into Zone 1 (high), Zone 2 (moderate), or Zone 3 (low) for radon. Plain-English guide to the classifications and at-home testing.
EPA SDWIS — how to read drinking-water violations and what they actually mean
Plain-English guide to EPA SDWIS drinking-water violations: health-based vs. monitoring vs. reporting violations, MCLs, and what triggers a public notice.
Radon and real estate — what disclosure laws and home tests actually require
What home sellers must disclose about radon by state, when home tests are required, and how to interpret radon-mitigation systems if a home you're buying has one.
Radon disclosure during real-estate transactions — state-by-state
Whether sellers must disclose known radon results varies by state. Quick map of mandatory-disclosure states + what to ask for during inspection.