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 Union County, Tennessee
EPA puts Union County in Zone 1, its highest radon zone, and only 3 radon tests from it are 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
37.7%
4.4 pts above TN
- Union
- 37.7%
- Tennessee
- 33.3%
53 tests, 2008 to 2017
Median result
2.1pCi/L
Below action level
- Union
- 2.1 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
53
63rd of 80 by tests
- Union
- 53
- 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
24 of 80
Middle half
- Union
- 37.7%
- Jefferson
- 56.8%
By share, of 80 with 30+ tests
Read a result for Union County
Starts at Union County's median, 2.1 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.1 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. Union County's median reported result, 2008 to 2017.
The data
Union County, At a glance
Union County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Union 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 Union County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2022 | 0.0% |
| 2023 | 33.3% |
2023: 33.3%. Across these years the share ran from 0.0% to 33.3%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 3 tests were reported to CDC for Union 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).
Union County, Compared
Union County radon figures, compared
Calculated by Radon411In Union County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (20 of 53) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 2.0 points higher. Across 95 Tennessee counties pooled together, 33.3% of tests reached that level, so Union County runs 4.4 points above its state.
The newest figure, in 2023, counts only 3 tests (33.3% at or above 4 pCi/L), too few to compare, so this reading uses the 53-test figure.
Of 5 neighbours with a figure, 4 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 33.6% (Knox County) to 53.5% (Campbell County). By share, Union County is 24th of 80 Tennessee counties with 30 or more tests for the same period.
Half the tests came in under 2.1 pCi/L and half over it; the single highest reached 97.5 pCi/L. Below the action level, 24 tests (45.3%) came in under 2 pCi/L, against 42.4% statewide, and 9 tests (17.0%) fell between 2 and 4, against 24.3% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 37.7% 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 21 tests reported; the quietest, 2023, had 3.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Union County, Geology
The ground under Union County
PredictedUSGS's geologic map puts all of Union County's mapped land in one class: high radon potential. All of it lies in the area the map calls Ridge and Valley, 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 |
|---|---|---|---|---|
| Ridge and Valley | Paleozoic sandstone and cherty dolostone. | High | 14 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Union County beside the ground around it
Union County has more high-potential ground than Tennessee as a whole: 100% of its land against 47.2%. Of the 5 counties that border it, none has as large a share of high-potential ground; Grainger County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Union County, Local resources
Radon testing and mitigation in Union 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
Union County, Questions
Questions about radon in Union County
Are radon levels high in Union County?
In 2023, 33.3% of the radon tests reported to CDC for Union County, Tennessee were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.8 pCi/L. Of 80 Tennessee counties with 30 or more tests for the same period, 23 reported a higher share; pooled, the state comes to 33.3%.
Which counties border Union County?
Union County borders 5 counties: Claiborne County, Grainger County, Campbell County, Knox County and Anderson County.
Products
Union County, Products
Testing a home in Union County
In Union County, 37.7% of 53 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 Union 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
Wave Plus battery radon and air quality monitor
- C-NRPP 2024/25: Not included
- Battery
- Bluetooth
- App only
Method: Alpha spectrometry
Short-term kitempowerDX
Standard Radon Test short-term mail-in radon test kit
- Lab fee included
Method: Passive sampler
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Union County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Union County
Explore
Union County, Bordering counties
Counties bordering Union County
Calculated by Radon411- Radon levels in Campbell CountyEPA zone 3
53.5%at or above 4 pCi/L
Median 4.5 pCi/L · 71 tests · 15.8 points above Union County
- Radon levels in Anderson CountyEPA zone 1
48.3%at or above 4 pCi/L
Median 3.8 pCi/L · 269 tests · 10.6 points above Union County
- Radon levels in Grainger CountyEPA zone 1
48.2%at or above 4 pCi/L
Median 3.8 pCi/L · 56 tests · 10.5 points above Union County
- Radon levels in Claiborne CountyEPA zone 1
44.0%at or above 4 pCi/L
Median 3.3 pCi/L · 125 tests · 6.3 points above Union County
- Radon levels in Knox CountyEPA zone 1
33.6%at or above 4 pCi/L
Median 2.5 pCi/L · 2,452 tests · 4.1 points below Union County
Union County, Cities and towns
Cities and towns in Union County
Union County is growing: the Census Bureau puts it at 21,450 residents on July 1, 2025, up 8.1% from 19,847 in 2020. That works out to 96 people per square mile of land. No town dominates: Maynardville, the largest, has 2,723 residents, 12.7% of the total. Together its 3 incorporated places hold 28.5% of those residents; the other 71.5% live outside any of them. Reported testing is thin here: 53 tests over 2008 to 2017, or 2.5 for every 1,000 residents (2025 estimate), where Tennessee as a whole comes to 4.2.
From Maynardville to Luttrell, CDC publishes no figure by town: each reads Union County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Maynardville | 2,723 | +9.9% | 12.7% |
| Plainview | 2,263 | +9.9% | 10.6% |
| Luttrell | 1,118 | +9.3% | 5.2% |
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).
Union County, Homes
Homes in Union County
Of Union County's 9,719 homes, 73% are detached houses, against 68% across Tennessee; 23% are mobile homes. Half of its homes were built before 1993, close to Tennessee's 1986: 13% date from before 1960 and 35% from 2000 or later. Owners live in 80% of the occupied homes (Tennessee: 67%), so for most households a test and a fix are their own to order.
| Homes | Union County | Tennessee |
|---|---|---|
| Housing units | 9,719 | 3,095,472 |
| Detached houses | 73% | 68% |
| In buildings of 5 or more | 2% | 14% |
| Mobile homes | 23% | 8% |
| Built before 1960 | 13% | 18% |
| Built since 2000 | 35% | 29% |
| Middle year built | 1993 | 1986 |
| Owner-occupied | 80% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.