Skip to content
RADON411

Locations and reports

Radon Levels in Richland County, South Carolina

EPA puts Richland County in Zone 3, its lowest radon zone, and most reported tests there come back low, though 4.9% of 671 (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

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    4.9%

    14.5 pts below SC

    Richland
    4.9%
    SC
    19.4%

    671 tests, 2008 to 2017

  • Median result

    0.7pCi/L

    Below action level

    Richland
    0.7 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    671

    7th of 24 by tests

    Richland
    671
    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

    18 of 24

    Middle half

    Richland
    4.9%
    Oconee
    42.6%

    By share, of 24 with 30+ tests

Read a result for Richland County

Starts at Richland 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. Richland County's median reported result, 2008 to 2017.

Interpret this reading

The data

Richland County, At a glance

Richland County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Richland 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 99% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

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

Reported results by concentration band, Richland County, 2008 to 2017, laboratory
Under 2 pCi/L: 86%2 to 4 pCi/L: 9%4 pCi/L and above: 5%

Of 671 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Richland County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L58086.4%
2 to 4 pCi/L588.6%
4 pCi/L and above334.9%
What these figures count

These are the 671 tests reported to CDC for Richland 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

Richland County, Compared

Richland County radon figures, compared

Calculated by Radon411

Only 33 of 671 radon tests reported for Richland County over the 2008 to 2017 laboratory totals reached 4 pCi/L (4.9%). 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 10.8 pCi/L.

Across 46 South Carolina counties pooled together, 19.4% of tests reached that level, so Richland County runs 14.5 points below its state. Against the national pool of 35.7%, the gap is 30.8 points lower. Its place in the state: 18th 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 4.9% share point the same way here. Of 4 neighbours with a figure, all 4 reported a larger share at or above 4 pCi/L; the spread is 5.0% (Kershaw County) to 16.0% (Newberry County).

Below the action level, 580 tests (86.4%) came in under 2 pCi/L, against 57.4% statewide, and 58 tests (8.6%) fell between 2 and 4, against 23.1% statewide. USGS geology rates 99% of the county's land low radon potential.

CDC's ten-year totals for Richland County went from 927 tests (2005 to 2014) to 671 (2008 to 2017), the share going from 3.7% to 4.9%.

Richland County against South Carolina, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Richland County
Richland County6714.9%0.7 pCi/LThis county
South Carolina, pooled46 counties, pooled26,48119.4%Not pooled+14.5 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+30.8 points
Oconee Countyhighest in the state2,46942.6%3.3 pCi/L+37.7 points
Florence Countylowest in the state590.0%0.7 pCi/L−4.9 points
Newberry County, SCborders it7516.0%1.1 pCi/L+11.1 points
Lexington County, SCborders it59112.5%0.9 pCi/L+7.6 points
Sumter County, SCborders it4211.9%1.3 pCi/L+7.0 points
Fairfield County, SCborders it277.4%0.9 pCi/L+2.5 points
Kershaw County, SCborders it605.0%0.7 pCi/L+0.1 points
Calhoun County, SCborders it110.0%0.6 pCi/L−4.9 points
Where Richland County's reported results fell, 2008 to 2017, laboratory, beside South Carolina and the United States
ResultRichland County testsRichland County shareSouth Carolina shareU.S. shareAgainst South Carolina
Under 2 pCi/L58086.4%57.4%39.6%+29.0 points
2 to 4 pCi/L588.6%23.1%24.7%−14.5 points
4 pCi/L and above334.9%19.4%35.7%−14.5 points
Richland 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
Sumter County13 of 244211.9%1.3 pCi/L
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
Richland 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 20176714.9%0.7 pCi/L10.8 pCi/L19.4%+0.7 points
2007 to 20169254.2%0.7 pCi/L12.6 pCi/L19.3%+0.2 points
2006 to 20159054.0%0.7 pCi/L127.3 pCi/L19.8%+0.3 points
2005 to 20149273.7%0.7 pCi/L127.3 pCi/L19.8%First on file

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

Richland County, Geology

The ground under Richland County

Predicted

Most of the ground under Richland County is one class on USGS's geologic map: 99.5% of its land is low radon potential, with 0.5% moderate. The map puts 76.0% of Richland County in the area it calls Upper and Middle Coastal Plain and 23.5% in Carolina Slate Belt, with one smaller area beside them. USGS gives both a radon index of 8, in the low band (5 to 8).

USGS's geologic areas under Richland County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Upper and Middle Coastal PlainTertiary coastal plain sandy and silty sediments and marsh deposits.Low876.0%
Carolina Slate Beltamphibolite, granitic gneiss, quartzite, muscovite schist, meta-argillite, metavolcanic rocks.Low823.5%
Carolina and Charlotte Belt GranitesGranite and granite gneissModerate110.5%

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

Richland County beside the ground around it

Across South Carolina 0.2% of the land is rated high; none of Richland County's is. Of the 6 counties that border it, 3 have more moderate-potential ground, Fairfield County the most at 20.8%.

Share of land by USGS radon potential: Richland County, the 6 counties bordering it and South Carolina
AreaEPA zoneLow potentialModerate potentialHigh potential
Richland CountyZone 399.5%0.5%None
Calhoun CountyZone 3100%NoneNone
Lexington CountyZone 3100%NoneNone
Fairfield CountyZone 379.2%20.8%None
Kershaw CountyZone 388.7%11.3%None
Sumter CountyZone 3100%NoneNone
Newberry CountyZone 381.0%19.0%None
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

Richland County, Local resources

Radon testing and mitigation in Richland County

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

What it means

Richland County, Questions

Questions about radon in Richland County

Are radon levels high in Richland County?

Over the 2008 to 2017 laboratory totals, 4.9% of the radon tests reported to CDC for Richland 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, 17 reported a higher share; pooled, the state comes to 19.4%.

Which counties border Richland County?

Richland County borders 6 counties: Calhoun County, Lexington County, Fairfield County, Kershaw County, Sumter County and Newberry County.

Products

Richland County, Products

Testing a home in Richland County

In Richland County, 4.9% of 671 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 Richland County.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Richland County homes, compared

Explore

Richland County, Bordering counties

Counties bordering Richland County

Calculated by Radon411

Richland County, Cities and towns

Cities and towns in Richland County

The Census Bureau estimates 434,956 residents in Richland County for July 1, 2025, 19,201 more than in 2020 (+4.6%). That works out to 574 people per square mile of land. Columbia, the largest place on its list (147,035 residents in all), extends beyond Richland County, so no share of the total is worked out for it. Reported testing is thin here: 671 tests over 2008 to 2017, or 1.5 for every 1,000 residents (2025 estimate), where South Carolina as a whole comes to 4.8.

From Columbia to Eastover, CDC publishes no figure by town: each reads Richland County's.

The cities and towns in Richland County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Columbiaextends beyond Richland County147,035+8.2%Counted whole
Cayceextends beyond Richland County13,680−0.7%Counted whole
Irmoextends beyond Richland County12,204+6.0%Counted whole
Forest Acres10,390−2.2%2.4%
Blythewoodextends beyond Richland County7,233+49.1%Counted whole
Arcadia Lakes852−2.0%0.2%
Eastover704+2.5%0.2%

7 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). A place that extends beyond Richland County is counted whole, so it has no share.

Richland County, Homes

Homes in Richland County

Of Richland County's 185,196 homes, 64% are detached houses, against 64% across South Carolina; 21% are in buildings of five or more homes. Half of its homes were built before 1989, close to South Carolina's 1991: 16% date from before 1960 and 34% from 2000 or later. 60% 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 Richland County, South Carolina, 2019 to 2023
HomesRichland CountySouth Carolina
Housing units185,1962,401,638
Detached houses64%64%
In buildings of 5 or more21%13%
Mobile homes5%15%
Built before 196016%13%
Built since 200034%35%
Middle year built19891991
Owner-occupied60%71%

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