Radon · ZIP 04101
Radon in Portland, ME
ZIP 04101 is in Cumberland County, Maine, which the EPA Map of Radon Zones places in Zone 1: highest potential, with a predicted average indoor radon screening level greater than 4 pCi/L. That is a county-wide estimate, not a reading from any home, and EPA advises testing every home whatever its zone.
Cumberland County, Maine
Zone 1 — highest potential
The EPA Map of Radon Zones classifies Cumberland County as Zone 1 — a predicted average indoor radon screening level greater than 4 pCi/L. This is a county-level, 1993-baseline planning classification, not a measurement of any individual address in ZIP 04101.
The Map of Radon Zones should not be used to determine if individual homes need to be tested. No matter where you live, test your home for radon — it's easy and inexpensive.
Next step for your own home
What this page shows
The county-level classification and EPA's own testing guidance for this ZIP's county — shown above.
Source & refresh
EPA Radon Zones. The EPA Map of Radon Zones was published in 1993 and EPA does not update it on a schedule, so the zone shown here is the current official one. Primary source →
Limitations specific to this source
Radon is a regional indicator. Address-level radon measurement requires an at-home test kit (often free from state health departments).
Maine context
Radon, lead in older housing, coastal flood
Maine has Zone 1 radon statewide. Older housing stock carries lead-paint + lead-service-line risk in Portland, Lewiston, Bangor. Coastal AE/VE FEMA zones face Risk Rating 2.0 premium increases.
See Maine 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.
The other dimensions for ZIP 04101
Radon is one of twelve public-records dimensions zipradar indexes per address. See the ZIP 04101 index for the other eleven — each with its own regulator, source and link:
All dimensions for Portland, ME →Frequently asked questions
What is the radon for ZIP 04101?
Cumberland County, Maine (which covers ZIP 04101) is classified as EPA Radon Zone 1 — a predicted average indoor radon screening level greater than 4 pCi/L. This is a county-level, 1993-baseline planning classification, not an address-level measurement. The Map of Radon Zones should not be used to determine if individual homes need to be tested. No matter where you live, test your home for radon — it's easy and inexpensive.
Where does the radon data come from?
Source: EPA Radon Zones. The EPA Map of Radon Zones was published in 1993 and EPA does not update it on a schedule, so the zone shown here is the current official one. The original is at https://www.epa.gov/radon/find-information-about-local-radon-zones-and-state-contact-information.
What are the limitations of radon data?
Radon is a regional indicator. Address-level radon measurement requires an at-home test kit (often free from state health departments).
Is ZIP 04101 (Portland) data current?
zipradar last checked this page against the source on 2026-09-24. The EPA Map of Radon Zones was published in 1993 and EPA does not update it on a schedule, so the zone shown here is the current official one. The ZIP 04101 overview at /zip/04101/ lists the other topics zipradar covers for this ZIP.