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Radon Levels in Franklin County, Maine

EPA puts Franklin County in Zone 1, its highest radon zone, and 29.1% of its 141 reported radon tests (2008 to 2017, laboratory totals) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

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  • Share at 4+ pCi/L

    29.1%

    8.5 pts below ME

    Franklin
    29.1%
    Maine
    37.6%

    141 tests, 2008 to 2017

  • Median result

    1.8pCi/L

    Below action level

    Franklin
    1.8 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    141

    13th of 16 by tests

    Franklin
    141
    Cumberland
    4,076

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Maine

    14 of 16

    Lowest quarter

    Franklin
    29.1%
    York
    48.4%

    By share, of 16 with 30+ tests

Read a result for Franklin County

Starts at Franklin County's median, 1.8 pCi/L

1.8pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 1.8 pCi/L

Below 2 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 4 and aboveEPA says fix it

This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Franklin County's median reported result, 2008 to 2017.

Interpret this reading

The data

Franklin County, At a glance

Franklin County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Franklin County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

USGS geologic potential: Moderate across 65% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Franklin County, 2008 to 2017, laboratory

Reported results by concentration band, Franklin County, 2008 to 2017, laboratory
Under 2 pCi/L: 50%2 to 4 pCi/L: 21%4 pCi/L and above: 29%

Of 141 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Franklin County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L7150.4%
2 to 4 pCi/L2920.6%
4 pCi/L and above4129.1%
What these figures count

These are the 141 tests reported to CDC for Franklin County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.

Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Franklin County, Compared

Franklin County radon figures, compared

Calculated by Radon411

Franklin County's 141 reported tests over the 2008 to 2017 laboratory totals had a middle value of 1.8 pCi/L and a maximum of 58.3 pCi/L, and 29.1% reached 4 pCi/L. Maine as a whole (16 Maine counties, pooled) comes to 37.6%: 8.5 points higher than here.

Among its state's counties it ranks 14th of 16 Maine counties with 30 or more tests for the same period. Statewide for the same period, York County reported the highest share (48.4%) and Penobscot County the lowest (16.4%).

Below the action level, 71 tests (50.4%) came in under 2 pCi/L, against 41.4% statewide, and 29 tests (20.6%) fell between 2 and 4, against 21.0% statewide. CDC's ten-year totals for Franklin County went from 100 tests (2005 to 2014) to 141 (2008 to 2017), the share going from 26.0% to 29.1%.

EPA's 1993 zone map puts Franklin County in Zone 1, a predicted county average above 4 pCi/L. USGS geology rates 65% of the county's land moderate radon potential.

Next door, the shares run from 18.8% in Somerset County to 43.1% in Oxford County, with Somerset County below Franklin County.

Franklin County against Maine, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Franklin County
Franklin County14129.1%1.8 pCi/LThis county
Maine, pooled16 counties, pooled11,82537.6%Not pooled+8.5 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+6.6 points
York Countyhighest in the state1,38948.4%3.7 pCi/L+19.3 points
Penobscot Countylowest in the state1,49116.4%0.8 pCi/L−12.7 points
Oxford County, MEborders it39243.1%3.3 pCi/L+14.0 points
Androscoggin County, MEborders it1,49736.9%2.8 pCi/L+7.8 points
Kennebec County, MEborders it69630.3%2.1 pCi/L+1.2 points
Somerset County, MEborders it8518.8%1.5 pCi/L−10.3 points
Where Franklin County's reported results fell, 2008 to 2017, laboratory, beside Maine and the United States
ResultFranklin County testsFranklin County shareMaine shareU.S. shareAgainst Maine
Under 2 pCi/L7150.4%41.4%39.6%+9.0 points
2 to 4 pCi/L2920.6%21.0%24.7%−0.4 points
4 pCi/L and above4129.1%37.6%35.7%−8.5 points
Franklin County ranked among the 16 Maine counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Hancock County6 of 1632739.1%2.6 pCi/L
Androscoggin County7 of 161,49736.9%2.8 pCi/L
Lincoln County8 of 1624635.8%2.5 pCi/L
Waldo County9 of 1620932.1%2.3 pCi/L
Kennebec County10 of 1669630.3%2.1 pCi/L
Sagadahoc County11 of 1628330.0%2.1 pCi/L
Washington County12 of 165429.6%1.6 pCi/L
Knox County13 of 1628729.6%2.3 pCi/L
Franklin County14 of 1614129.1%1.8 pCi/L
Somerset County15 of 168518.8%1.5 pCi/L
Penobscot County16 of 161,49116.4%0.8 pCi/L
Franklin County ten-year laboratory totals, against Maine's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestMaine, pooledChange from the row before
2008 to 201714129.1%1.8 pCi/L58.3 pCi/L37.6%+1.2 points
2007 to 201613627.9%1.8 pCi/L58.3 pCi/L37.6%−0.9 points
2006 to 201511828.8%2.0 pCi/L58.3 pCi/L37.6%+2.8 points
2005 to 201410026.0%1.8 pCi/L58.3 pCi/L36.6%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Franklin County, Geology

The ground under Franklin County

Predicted

USGS's geologic map splits Franklin County: 65.1% of its land is moderate radon potential and 34.5% high and 0.3% low. The map puts 65.1% of Franklin County in the area it calls Moose River Lowlands/Central Maine Lowlands/Central Maine Highlands/Coastal Province and 33.2% in Moose River Lowlands/Central Maine Lowlands/Central Maine Highlands/Coastal Province, with one smaller area beside them. USGS gives the first a radon index of 11, in the moderate band (9 to 11), and the second 14, in the high band (12 to 17).

USGS's geologic areas under Franklin County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Moose River Lowlands/Central Maine Lowlands/Central Maine Highlands/Coastal ProvinceHeterogeneous metamorphic and igneous rocks.Moderate1165.1%
Moose River Lowlands/Central Maine Lowlands/Central Maine Highlands/Coastal ProvinceGranite and high grade metamorphic rocks.High1433.2%
Central Maine HighlandsClastic and carbonate sedimentary rocks.High141.3%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Franklin County beside the ground around it

Franklin County has more high-potential ground than Maine as a whole: 34.5% of its land against 24.5%. Of the 4 counties that border it, 3 have more high-potential ground, Oxford County the most at 85.1%.

Share of land by USGS radon potential: Franklin County, the 4 counties bordering it and Maine
AreaEPA zoneLow potentialModerate potentialHigh potential
Franklin CountyZone 10.3%65.1%34.5%
Oxford CountyZone 1None14.9%85.1%
Somerset CountyZone 145.6%52.3%2.1%
Kennebec CountyZone 130.4%32.7%36.9%
Androscoggin CountyZone 132.3%None67.7%
Maine16 counties, pooled by land areaVaries35.9%38.3%24.5%

The map rates the ground, not the air in any home.

Local help

Franklin County, Local resources

Radon testing and mitigation in Franklin County

What Maine's program says
Phone
207-287-5676
Email
radon.dhhs@maine.gov
Licensing of radon professionals
Under Maine law, only the owner or occupant of a residence or someone registered with the state to provide these services, may test for radon, install and/or advise on the installation of a radon reduction (mitigation) system.

What it means

Franklin County, Questions

Questions about radon in Franklin County

Are radon levels high in Franklin County?

Over the 2008 to 2017 laboratory totals, 29.1% of the radon tests reported to CDC for Franklin County, Maine were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.8 pCi/L. Of 16 Maine counties with 30 or more tests for the same period, 13 reported a higher share; pooled, the state comes to 37.6%.

Which counties border Franklin County?

Franklin County borders 4 counties: Oxford County, Somerset County, Kennebec County and Androscoggin County.

Products

Franklin County, Products

Testing a home in Franklin County

In Franklin County, 29.1% of 141 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 37.6% pooled across Maine. In Zone 1 the year-round level in Franklin County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.

Test kits and monitors3

See every kit and monitor

Franklin County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Franklin County

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Franklin County, Bordering counties

Counties bordering Franklin County

Calculated by Radon411

Franklin County, Residents

Who lives in Franklin County

The Census Bureau estimates 30,824 residents in Franklin County for July 1, 2025, 1,361 more than in 2020 (+4.6%). That works out to 18 people per square mile of land. Reported testing is thin here: 141 tests over 2008 to 2017, or 4.6 for every 1,000 residents (2025 estimate), where Maine as a whole comes to 8.4.

Census lists no incorporated place in Franklin County: every home in it reads the county's figures.

Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).

Franklin County, Homes

Homes in Franklin County

Franklin County is a place of houses on their own lots: 75% of its 21,089 homes are detached single-family houses, against 70% across Maine. Half of its homes were built before 1978, close to Maine's 1976: 28% date from before 1960 and 18% from 2000 or later. Owners live in 77% of the occupied homes (Maine: 74%), so for most households a test and a fix are their own to order.

Homes in Franklin County, Maine, 2019 to 2023
HomesFranklin CountyMaine
Housing units21,089746,552
Detached houses75%70%
In buildings of 5 or more8%9%
Mobile homes9%8%
Built before 196028%35%
Built since 200018%20%
Middle year built19781976
Owner-occupied77%74%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.