Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Smith County, Tennessee
EPA puts Smith County in Zone 1, its highest radon zone, and only 1 radon test from it is on file with CDC (2023). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
45.5%
12.2 pts above TN
- Smith
- 45.5%
- Tennessee
- 33.3%
55 tests, 2008 to 2017
Median result
3.1pCi/L
Below action level
- Smith
- 3.1 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
55
62nd of 80 by tests
- Smith
- 55
- Davidson
- 5,592
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Tennessee
16 of 80
Top quarter
- Smith
- 45.5%
- Jefferson
- 56.8%
By share, of 80 with 30+ tests
Read a result for Smith County
Starts at Smith County's median, 3.1 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 3.1 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Smith County's median reported result, 2008 to 2017.
The data
Smith County, At a glance
Smith County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Smith County in
USGS geologic potential: High across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Smith County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2022 | 20.0% |
| 2023 | 0.0% |
2023: 0.0%. Across these years the share ran from 0.0% to 20.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 1 test was reported to CDC for Smith County over 2023, and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.
Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).
Smith County, Compared
Smith County radon figures, compared
Calculated by Radon411In Smith County, about 5 in 10 reported tests over the 2008 to 2017 laboratory totals (25 of 55) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 9.8 points higher. Across 95 Tennessee counties pooled together, 33.3% of tests reached that level, so Smith County runs 12.2 points above its state.
The newest figure, in 2023, counts only 1 test (0.0% at or above 4 pCi/L), too few to compare, so this reading uses the 55-test figure.
Of 6 neighbours with a figure, 1 reported a larger share at or above 4 pCi/L and 5 a smaller one; the spread is 19.4% (Macon County) to 46.9% (Jackson County). By share, Smith County is 16th of 80 Tennessee counties with 30 or more tests for the same period.
Half the tests came in under 3.1 pCi/L and half over it; the single highest reached 157.8 pCi/L. Below the action level, 21 tests (38.2%) came in under 2 pCi/L, against 42.4% statewide, and 9 tests (16.4%) fell between 2 and 4, against 24.3% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 45.5% share point the same way here. USGS geology rates 100% of the county's land high radon potential.
The busiest year on file was 2022, with 15 tests reported; the quietest, 2023, had 1.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Smith County, Geology
The ground under Smith County
PredictedUSGS's geologic map puts all of Smith County's mapped land in one class: high radon potential. 96.6% of it lies in the area the map calls Nashville Basin, to which USGS gives a radon index of 14, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Nashville Basin | Mississippian Limestone. | High | 14 | 96.6% |
| Cherty Highland | Cherty dolostone. | High | 12 | 3.4% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Smith County beside the ground around it
Smith County has more high-potential ground than Tennessee as a whole: 100% of its land against 47.2%. Of the 6 counties that border it, none has as large a share of high-potential ground; Macon County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Smith County, Local resources
Radon testing and mitigation in Smith County
- Tennessee Radon ProgramTennessee Radon Program, run by Department of Environment & Conservation, offers free or discounted test kits, and answers questions about testing and mitigation in Tennessee.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
The Tennessee Radon Program provides free radon test kits and information assistance to residents, while also providing training opportunities to radon professionals across the state.
- Compare kits
- Professionals in Tennessee1 professional is listed in Tennessee.
What Tennessee's program says
- Phone
- 1-800-232-1139
- TDEC.Radon@tn.gov
What it means
Smith County, Questions
Questions about radon in Smith County
Are radon levels high in Smith County?
In 2023, 0.0% of the radon tests reported to CDC for Smith County, Tennessee were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.9 pCi/L. Of 80 Tennessee counties with 30 or more tests for the same period, 15 reported a higher share; pooled, the state comes to 33.3%.
Which counties border Smith County?
Smith County borders 6 counties: Trousdale County, Jackson County, Macon County, Wilson County, DeKalb County and Putnam County.
Products
Smith County, Products
Testing a home in Smith County
In Smith County, 45.5% of 55 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 33.3% pooled across Tennessee. In Zone 1 the year-round level in Smith 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
Monitor
Corentium Home battery digital radon detector
- C-NRPP 2024/25: Approved
- Battery
- Screen
Method: Alpha spectrometry
Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
Method: Liquid scintillation
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Smith County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Smith County
Explore
Smith County, Bordering counties
Counties bordering Smith County
Calculated by Radon411- Radon levels in Jackson CountyEPA zone 1
46.9%at or above 4 pCi/L
Median 3.9 pCi/L · 49 tests · 1.4 points above Smith County
- Radon levels in Putnam CountyEPA zone 2
36.0%at or above 4 pCi/L
Median 2.6 pCi/L · 336 tests · 9.5 points below Smith County
- Radon levels in DeKalb CountyEPA zone 2
30.5%at or above 4 pCi/L
Median 3.1 pCi/L · 59 tests · 15.0 points below Smith County
- Radon levels in Trousdale CountyEPA zone 1
27.3%at or above 4 pCi/L
Median 1.8 pCi/L · 33 tests · 18.2 points below Smith County
- Radon levels in Wilson CountyEPA zone 1
20.2%at or above 4 pCi/L
Median 1.7 pCi/L · 959 tests · 25.3 points below Smith County
- Radon levels in Macon CountyEPA zone 1
19.4%at or above 4 pCi/L
Median 1.9 pCi/L · 67 tests · 26.1 points below Smith County
Smith County, Cities and towns
Cities and towns in Smith County
Smith County is growing: the Census Bureau puts it at 20,981 residents on July 1, 2025, up 5.1% from 19,963 in 2020. That works out to 67 people per square mile of land. No town dominates: Carthage, the largest, has 2,282 residents, 10.9% of the total. Together its 3 incorporated places hold 25.4% of those residents; the other 74.6% live outside any of them. Reported testing is thin here: 55 tests over 2008 to 2017, or 2.6 for every 1,000 residents (2025 estimate), where Tennessee as a whole comes to 4.2.
From Carthage to Gordonsville, CDC publishes no figure by town: each reads Smith County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Carthage | 2,282 | −0.2% | 10.9% |
| South Carthage | 1,576 | +5.8% | 7.5% |
| Gordonsville | 1,464 | +6.9% | 7.0% |
3 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).
Smith County, Homes
Homes in Smith County
Of Smith County's 8,649 homes, 73% are detached houses, against 68% across Tennessee; 19% are mobile homes. Half of its homes were built before 1985, close to Tennessee's 1986: 21% date from before 1960 and 22% from 2000 or later. Owners live in 75% of the occupied homes (Tennessee: 67%), so for most households a test and a fix are their own to order.
| Homes | Smith County | Tennessee |
|---|---|---|
| Housing units | 8,649 | 3,095,472 |
| Detached houses | 73% | 68% |
| In buildings of 5 or more | 4% | 14% |
| Mobile homes | 19% | 8% |
| Built before 1960 | 21% | 18% |
| Built since 2000 | 22% | 29% |
| Middle year built | 1985 | 1986 |
| Owner-occupied | 75% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.