Radon levels in Maine: Moderate
The model predicts a population-weighted basement average of 2.2 pCi/L (model estimate) across Maine's 16 counties - about 1.2× the US average of 1.8 pCi/L. Above-ground floors average 1.2 pCi/L.
Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.
12 / 16
EPA Zone 1 counties (75%)
4 / 0
Zone 2 / Zone 3 counties
0
counties predicted ≥ 4 pCi/L
0%
of ZIP codes predicted ≥ 4 pCi/L
Test Maine - the EPA says "consider fixing" in this range
The predicted basement average here is 2.2 pCi/L, in the 2-4 pCi/L band where the EPA recommends considering mitigation. Plenty of individual homes in a moderate area test above 4. Start with a short-term test; if it comes back at 2 or higher, follow up with a long-term test or a continuous monitor.
Monitor link goes to the Airthings store - use code RADONGRADE-10OFF at checkout for 10% off any Airthings monitor.
Already tested at 4 pCi/L or higher? Find a certified mitigation professional (EPA). A mitigation system typically runs $800-$2,500 installed.
Affiliate links: we may earn a commission from Airthings or Amazon at no extra cost to you.
What the data says about radon in Maine
12 of Maine's 16 counties are EPA Zone 1 (75%), 4 are Zone 2 and 0 are Zone 3 on the EPA's county-level map. Zone 1 - the highest-potential class, predicted screening average above 4 pCi/L - is the most common designation in Maine. The zones were drawn once, from geology and the tests available in 1993, and the EPA itself notes that homes with elevated radon exist in all three zones.
Weighted by where people live, Maine's predicted basement average is 2.2 pCi/L - 1.2× the US population-weighted average of 1.8 - which puts the state in the moderate range. Of the 16 counties with predictions, 0 are predicted at or above 4 pCi/L, 8 in the 2-4 band and 8 below 2. The county range is narrow: from Penobscot County at 1.74 to Oxford County at 2.64 pCi/L, a spread of only 0.90.
Nationally 4.2% of ZIPs are predicted at 4+ pCi/L and 48.7% at 2+; in Maine it is 0% and 54% - below the US share at the action level but near it at 2 pCi/L. With more than half of ZIPs above 2, a test is worth doing before any purchase or renovation here.
Maine counties by predicted radon
Sorted highest to lowest predicted basement average (model estimate). 16 counties.
| County | Predicted basement | Upstairs | Grade | EPA zone | ZIPs |
|---|---|---|---|---|---|
| Oxford County | 2.6 pCi/L | 1.6 | Moderate | EPA Zone 1 | 29 |
| York County | 2.5 pCi/L | 1.6 | Moderate | EPA Zone 1 | 32 |
| Franklin County | 2.4 pCi/L | 1.4 | Moderate | EPA Zone 1 | 13 |
| Cumberland County | 2.3 pCi/L | 1.5 | Moderate | EPA Zone 1 | 36 |
| Knox County | 2.3 pCi/L | 1.4 | Moderate | EPA Zone 2 | 18 |
| Hancock County | 2.2 pCi/L | 1.3 | Moderate | EPA Zone 1 | 37 |
| Aroostook County | 2.2 pCi/L | 1.1 | Moderate | EPA Zone 1 | 40 |
| Waldo County | 2.1 pCi/L | 1.3 | Moderate | EPA Zone 2 | 18 |
| Androscoggin County | 1.9 pCi/L | 0.9 | Low | EPA Zone 1 | 14 |
| Kennebec County | 1.9 pCi/L | 0.9 | Low | EPA Zone 1 | 23 |
| Lincoln County | 1.9 pCi/L | 0.9 | Low | EPA Zone 1 | 24 |
| Somerset County | 1.9 pCi/L | 1.0 | Low | EPA Zone 1 | 23 |
| Piscataquis County | 1.9 pCi/L | 1.0 | Low | EPA Zone 1 | 11 |
| Washington County | 1.9 pCi/L | 0.9 | Low | EPA Zone 2 | 31 |
| Sagadahoc County | 1.8 pCi/L | 0.8 | Low | EPA Zone 2 | 8 |
| Penobscot County | 1.7 pCi/L | 0.8 | Low | EPA Zone 1 | 39 |
Radon levels in Maine cities
The one most-populous Maine place among the 1,000 largest US cities (Census incorporated places and CDPs), by population. City figures are ZIP-land-weighted means of the model's ZIP predictions (model estimate).
| City | Population | Predicted basement | Upstairs | Grade | ZIPs ≥ 4 |
|---|---|---|---|---|---|
| Portland | 69,104 | 2.1 pCi/L | 1.4 | Moderate | 0% |
Highest-radon ZIP codes in Maine
The 10 Maine ZIP codes with the highest predicted basement average (model estimate), out of 396 modeled. A ZIP average is still an area figure - neighboring homes routinely test several pCi/L apart.
| ZIP | County | Predicted basement | Upstairs | Grade |
|---|---|---|---|---|
| 04062 | Cumberland County | 3.8 pCi/L | 2.0 | Moderate |
| 04071 | Cumberland County | 3.6 pCi/L | 2.1 | Moderate |
| 04084 | Cumberland County | 3.1 pCi/L | 2.0 | Moderate |
| 04073 | York County | 3.0 pCi/L | 1.7 | Moderate |
| 04268 | Oxford County | 3.0 pCi/L | 1.7 | Moderate |
| 03902 | York County | 3.0 pCi/L | 1.8 | Moderate |
| 04217 | Oxford County | 3.0 pCi/L | 1.6 | Moderate |
| 04736 | Aroostook County | 3.0 pCi/L | 1.0 | Moderate |
| 04274 | Androscoggin County | 2.9 pCi/L | 1.7 | Moderate |
| 04105 | Cumberland County | 2.9 pCi/L | 1.8 | Moderate |
Maine radon questions
- Is radon high in Maine?
- Maine's population-weighted predicted basement average is 2.2 pCi/L, about 1.2× the US average of 1.8. 0 of its 16 modeled counties are predicted at or above the EPA action level of 4 pCi/L, 8 are in the 2-4 "consider fixing" range and 8 are below 2. 0% of Maine ZIP codes are predicted at 4 or higher.
- Which Maine county has the highest radon?
- Oxford County has the highest predicted basement average in Maine at 2.6 pCi/L (EPA Zone 1). The lowest is Penobscot County at 1.7 pCi/L. These are area figures; individual homes in any county can test far higher.
- How many EPA Zone 1 counties are in Maine?
- 12 of Maine's 16 counties (75%) are EPA Zone 1 (highest potential), 4 are Zone 2 and 0 are Zone 3. The EPA zone map dates from 1993; the predicted values on this page come from a 2001-2021 model built on millions of actual tests, so the two can disagree for a given county.
- Should I test for radon in Maine?
- Yes - with some urgency. Maine's predicted average is in the moderate range, and 54% of its ZIP codes are predicted at 2 pCi/L or higher. A short-term charcoal kit or a continuous digital monitor will tell you your actual level within days.
Maine radon program
State programs keep lists of certified testers and mitigators and sometimes run kit programs. We link only pages we could verify, and Maine's program page did not respond when we checked, so start from the EPA state radon contacts page. Then read how to test and what mitigation costs.