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Radon Levels in Florence County, South Carolina

EPA puts Florence County in Zone 3, its lowest radon zone, and most reported tests there come back low, though 0.0% of 59 (2008 to 2017, laboratory totals) reached 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

    0.0%

    19.4 pts below SC

    Florence
    0.0%
    SC
    19.4%

    59 tests, 2008 to 2017

  • Median result

    0.7pCi/L

    Below action level

    Florence
    0.7 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    59

    22nd of 24 by tests

    Florence
    59
    Greenville
    12,004

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 3

    Lower potential

    1. 1
    2. 2
    3. Zone 3

    1 highest, 3 lowest

    EPA predicts under 2 pCi/L indoors

  • Rank in SC

    24 of 24

    Lowest quarter

    Florence
    0.0%
    Oconee
    42.6%

    By share, of 24 with 30+ tests

Read a result for Florence County

Starts at Florence County's median, 0.7 pCi/L

0.7pCi/L

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

EPA’s reading of 0.7 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. Florence County's median reported result, 2008 to 2017.

Interpret this reading

The data

Florence County, At a glance

Florence County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Florence County as a whole is an average indoor of less than 2 pCi/L (less than 75 Bq/m³). A low zone clears no address in it: homes above EPA's turn up in all three zones.

USGS geologic potential: Low across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

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

Reported results by concentration band, Florence County, 2008 to 2017, laboratory
Under 2 pCi/L: 97%2 to 4 pCi/L: 3%4 pCi/L and above: 0%

Of 59 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Florence County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L5796.6%
2 to 4 pCi/L23.4%
4 pCi/L and above00.0%
What these figures count

These are the 59 tests reported to CDC for Florence 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

Florence County, Compared

Florence County radon figures, compared

Calculated by Radon411

Only 0 of 59 radon tests reported for Florence County over the 2008 to 2017 laboratory totals reached 4 pCi/L (0.0%). The median result, 0.7 pCi/L, sits below 2, well under EPA's 4 pCi/L action level, and the top reported result was 2.6 pCi/L.

Across 46 South Carolina counties pooled together, 19.4% of tests reached that level, so Florence County runs 19.4 points below its state. Against the national pool of 35.7%, the gap is 35.7 points lower. Its place in the state: 24th of 24 South Carolina counties with 30 or more tests for the same period.

Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 0.0% share point the same way here. Sumter County, the one bordering county with a figure for the same period, reported 11.9%.

Below the action level, 57 tests (96.6%) came in under 2 pCi/L, against 57.4% statewide, and 2 tests (3.4%) fell between 2 and 4, against 23.1% statewide. USGS geology rates 100% of the county's land low radon potential.

CDC's ten-year totals for Florence County went from 56 tests (2005 to 2014) to 59 (2008 to 2017), the share going from 1.8% to 0.0%.

Florence County against South Carolina, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Florence County
Florence County590.0%0.7 pCi/LThis county
South Carolina, pooled46 counties, pooled26,48119.4%Not pooled+19.4 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+35.7 points
Oconee Countyhighest in the state2,46942.6%3.3 pCi/L+42.6 points
Horry Countylowest in the state1060.9%0.6 pCi/L+0.9 points
Sumter County, SCborders it4211.9%1.3 pCi/L+11.9 points
Clarendon County, SCborders it30.0%0.8 pCi/LLevel
Darlington County, SCborders it280.0%0.6 pCi/LLevel
Dillon County, SCborders it180.0%0.3 pCi/LLevel
Lee County, SCborders it30.0%1.1 pCi/LLevel
Williamsburg County, SCborders it140.0%0.6 pCi/LLevel
Marlboro County, SCborders it70.0%0.9 pCi/LLevel
Marion County, SCborders it90.0%0.9 pCi/LLevel
Where Florence County's reported results fell, 2008 to 2017, laboratory, beside South Carolina and the United States
ResultFlorence County testsFlorence County shareSouth Carolina shareU.S. shareAgainst South Carolina
Under 2 pCi/L5796.6%57.4%39.6%+39.2 points
2 to 4 pCi/L23.4%23.1%24.7%−19.7 points
4 pCi/L and above00.0%19.4%35.7%−19.4 points
Florence County ranked among the 24 South Carolina counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Anderson County14 of 241,73311.1%1.1 pCi/L
Greenwood County15 of 241137.1%1.0 pCi/L
Orangeburg County16 of 24535.7%0.9 pCi/L
Kershaw County17 of 24605.0%0.7 pCi/L
Richland County18 of 246714.9%0.7 pCi/L
Dorchester County19 of 241044.8%1.0 pCi/L
Berkeley County20 of 24994.0%0.7 pCi/L
Beaufort County21 of 242462.0%0.7 pCi/L
Charleston County22 of 242721.5%0.6 pCi/L
Horry County23 of 241060.9%0.6 pCi/L
Florence County24 of 24590.0%0.7 pCi/L
Florence County ten-year laboratory totals, against South Carolina's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestSouth Carolina, pooledChange from the row before
2008 to 2017590.0%0.7 pCi/L2.6 pCi/L19.4%Level
2007 to 2016540.0%0.6 pCi/L2.6 pCi/L19.3%Level
2006 to 2015560.0%0.8 pCi/L2.6 pCi/L19.8%−1.8 points
2005 to 2014561.8%0.8 pCi/L6.8 pCi/L19.8%First on file

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

Florence County, Geology

The ground under Florence County

Predicted

USGS's geologic map puts all of Florence County's mapped land in one class: low radon potential. The map puts 92.9% of Florence County in the area it calls Upper and Middle Coastal Plain and 7.1% in Lower Coastal Plain. USGS gives the first a radon index of 8 and the second 7, both in the low band (5 to 8).

USGS's geologic areas under Florence County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Upper and Middle Coastal PlainTertiary coastal plain sandy and silty sediments and marsh deposits.Low892.9%
Lower Coastal PlainDune, beach, and marine sediments.Low77.1%

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

Florence County beside the ground around it

Across South Carolina 0.2% of the land is rated high; none of Florence County's is. None of the 8 counties that border it has any moderate-potential ground either.

Share of land by USGS radon potential: Florence County, the 8 counties bordering it and South Carolina
AreaEPA zoneLow potentialModerate potentialHigh potential
Florence CountyZone 3100%NoneNone
Marion CountyZone 3100%NoneNone
Darlington CountyZone 3100%NoneNone
Williamsburg CountyZone 3100%NoneNone
Dillon CountyZone 3100%NoneNone
Lee CountyZone 3100%NoneNone
Sumter CountyZone 3100%NoneNone
Clarendon CountyZone 3100%NoneNone
Marlboro CountyZone 3100%NoneNone
South Carolina46 counties, pooled by land areaVaries80.8%18.2%0.2%

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

Local help

Florence County, Local resources

Radon testing and mitigation in Florence County

What South Carolina's program says
Phone
1-800-768-0362
Email
radon@des.sc.gov

What it means

Florence County, Questions

Questions about radon in Florence County

Are radon levels high in Florence County?

Over the 2008 to 2017 laboratory totals, 0.0% of the radon tests reported to CDC for Florence County, South Carolina were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.7 pCi/L. Of 24 South Carolina counties with 30 or more tests for the same period, 23 reported a higher share; pooled, the state comes to 19.4%.

Which counties border Florence County?

Florence County borders 8 counties: Marion County, Darlington County, Williamsburg County, Dillon County, Lee County, Sumter County, Clarendon County and Marlboro County.

Products

Florence County, Products

Testing a home in Florence County

In Florence County, 0.0% of 59 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 19.4% pooled across South Carolina. Zone 3 is the lowest label, yet homes at or above 4 pCi/L occur in every zone: a short-term kit (2 to 90 days) is the quick first check in Florence County.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Florence County homes, compared

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Florence County, Bordering counties

Counties bordering Florence County

Calculated by Radon411

Florence County, Cities and towns

Cities and towns in Florence County

The Census Bureau estimates 138,504 residents in Florence County for July 1, 2025, 1,678 more than in 2020 (+1.2%). That works out to 173 people per square mile of land. Its largest town, Florence, has 41,231 residents, 29.8% of the total. Together its 9 incorporated places hold 39.4% of those residents; the other 60.6% live outside any of them. Reported testing is thin here: 59 tests over 2008 to 2017, or 0.4 for every 1,000 residents (2025 estimate), where South Carolina as a whole comes to 4.8.

From Florence to Olanta, CDC publishes no figure by town: each reads Florence County's.

The cities and towns in Florence County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Florence41,231+3.2%29.8%
Lake City5,940−1.4%4.3%
Timmonsville2,117+1.1%1.5%
Johnsonville1,348−0.7%1.0%
Pamplico1,062+0.2%0.8%
Quinby883−0.9%0.6%
Coward729+0.7%0.5%
Scranton653−0.3%0.5%
Olanta550−0.7%0.4%

9 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).

Florence County, Homes

Homes in Florence County

Of Florence County's 61,418 homes, 62% are detached houses, against 64% across South Carolina; 19% are mobile homes. Half of its homes were built before 1985, close to South Carolina's 1991: 15% date from before 1960 and 25% from 2000 or later. 65% of occupied homes are lived in by their owner (South Carolina: 71%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Florence County, South Carolina, 2019 to 2023
HomesFlorence CountySouth Carolina
Housing units61,4182,401,638
Detached houses62%64%
In buildings of 5 or more10%13%
Mobile homes19%15%
Built before 196015%13%
Built since 200025%35%
Middle year built19851991
Owner-occupied65%71%

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