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Radon Levels in Johnson County, Tennessee

Zone 2Moderate predicted potential306 square miles · 7 bordering counties

What this means for you

  • Your area: EPA rates Johnson County Zone 2, the middle of its three radon zones. That is a prediction for the whole county, and homes with elevated levels occur in all three zones.
  • Local tests: Of 5 buildings with radon tests reported to CDC for Johnson County (2023), 50.0% were at or above 4 pCi/L, EPA's action level.
  • Your home: The only way to know your home’s level is to test it.

pCi/L (picocuries per liter) is the unit radon is measured in. EPA recommends fixing a home at 4 pCi/L or above, its action level.

In 2023, 50.0% of the radon tests reported to CDC for Johnson County, Tennessee came back at or above the EPA action level of 4 pCi/L, and the median result was 4.7 pCi/L. EPA's Map of Radon Zones places the county in Zone 2, moderate predicted potential. Radon levels vary from home to home, so only a test measures the level in yours.

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

EPA predicts an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³) across the county as a whole.

This is a county-level geologic prediction. It is not a measurement of any address, and houses with elevated radon are found in all three zones.

USGS geologic potential: Low across 85% of the county's land area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Johnson County, 2023

Buildings tested
5
At or above 4 pCi/L
50.0%
Median result
4.7 pCi/L

Distribution of tested buildings, not this house. People testing before a sale, or because they suspect a problem, are over-represented in any reported testing data.

Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).

Johnson County, In figures

Johnson County in figures

What the published data says about Johnson County, in words. A zone and a share of tests describe an area, never the level in any one home.

    • Predicted

      Predicted

      EPA places Johnson County in Zone 2, moderate predicted potential, as it does 31 other counties of Tennessee's 95.

      Of the 7 bordering counties, EPA places Sullivan County, Washington County and Watauga County in Zone 1 and Ashe County, Avery County, Carter County and Grayson County in Zone 2.

  • Reported tests

    Measured

    CDC has annual figures for Johnson County for 2 years, 2022 to 2023. In 2023, 50.0% of reported tests were at or above 4 pCi/L.

  • Local record

    Tennessee's radon program is the Tennessee Radon Program, run by Department of Environment & Conservation; its contacts are under Local resources.

    The county's largest incorporated place is Mountain City; the figures here cover them as part of the county.

Johnson County, Reported testing

Reported testing over time

Measured
Reported radon test results by year, Johnson County, pCi/LLogarithmic scale: each step up the axis multiplies the level, so the median and the single highest result can share one chart. The darker gridline is EPA's action level, 4 pCi/L.
Median reported resultHighest reported result
Reported radon test results by year, Johnson County, pCi/L: data table
YearMedian reported resultHighest reported resultShare of tests at or above 4 pCi/L
20220.9 pCi/L14.7 pCi/L36.4%
20234.7 pCi/L6.4 pCi/L50.0%

What these figures count

Every percentage here is a share of radon tests reported to CDC for Johnson County in 2023. It is not a share of homes in Johnson County, and it is not a random sample: it counts only the tests people chose to run and that were reported.

The shares and the median are calculated from pre-mitigation tests. CDC also reports the number of buildings tested (5), a different count, so the two totals are not interchangeable.

Johnson County, Comparison

How Johnson County compares

Measured

Johnson County's own published CDC figures beside those of the counties that border it, for the same period.

Share of reported tests at or above 4 pCi/L

Measured

2023, highest first. Each county’s own published CDC figure.

  1. Johnson CountyThis pageTest count not published50.0%
  2. Sullivan CountyTN27 tests37.0%

Published for 2023 without this measure: Carter County, TN.

Median reported result

Measured

2023, highest first. Each county’s own published CDC figure.

  1. Johnson CountyThis pageTest count not published4.7 pCi/L
  2. Sullivan CountyTN27 tests2.6 pCi/L
  3. Carter CountyTNTest count not published1.2 pCi/L

Each figure is that county’s own published CDC figure for 2023, counting radon tests reported to CDC, not homes. Johnson County is this page. Nothing is averaged or combined across counties. The test count beside each county is CDC’s published number of pre-mitigation tests behind its figures. Figures from few tests can swing widely from year to year. No published CDC figure for 2023: Watauga County, NC; Ashe County, NC; Washington County, VA; Avery County, NC; Grayson County, VA. Every Tennessee county’s own figure is in the Tennessee county table.

CDC publishes this figure only for counties here, so there is no state or national number to compare Johnson County, Tennessee with.

Johnson County, Bordering counties

Counties bordering Johnson County

Calculated by Radon411

Johnson County, Local resources

Local resources in Tennessee

Who to ask in Tennessee: the state's radon program, test kits and professionals.

Tennessee Radon Program

Department of Environment & Conservation

Tennessee’s radon program answers questions about testing, mitigation and the rules where you live.

Phone
1-800-232-1139
Email
TDEC.Radon@tn.gov
Visit the program's page(opens in a new tab)

Test kits

The 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.

Radon professionals

1 professional is listed in Tennessee.

Professionals in Tennessee

Johnson County, Cities and towns

Cities and towns in Johnson County

The radon figures on this page are for Johnson County as a whole. They do not differ by city or town.

  • Mountain City

One incorporated place, as listed in the U.S. Census Bureau’s 2020 place reference files.

Johnson County, Questions

Questions about radon in Johnson County

Common questions8 questions, answered from the figures above

Who does radon mitigation in Johnson County?

No listed mitigator names Johnson County as a service area yet; the Tennessee directory lists 1 company. EPA recommends having a qualified contractor fix a home with a radon problem, because lowering high radon levels takes technical knowledge and special skills, and some states require the work to be done by a licensed or certified professional. Your state radon program is the place to check whether Tennessee requires one.

How radon mitigation worksWhat mitigation costsMitigators in Tennessee

How do I get a radon test in Johnson County?

EPA says you can test your home yourself or hire a qualified radon test company, and that either approach takes only a small amount of time and effort. No certified tester listed on Radon411 names Johnson County as a service area yet. The Tennessee radon program is the place to ask about certified testers and any test kit offer it runs.

How to test a homeTest kits comparedFree and low-cost kits by stateTennessee radon program

Are radon levels high in Johnson County?

In 2023, 50.0% of the radon tests reported to CDC for Johnson County, Tennessee were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.7 pCi/L. That is a share of reported tests, not of homes. EPA places Johnson County in Zone 2, moderate predicted potential, a predicted average indoor screening level 2 to 4 pCi/L. Homes with elevated levels occur in all three zones, so the figures describe the area, not your house. Testing is the only way to know the radon level in a specific building.

What a radon level meansRadon in Tennessee

What EPA radon zone is Johnson County in?

EPA places Johnson County, Tennessee in Zone 2, which EPA describes as moderate predicted potential for the area. A zone is a prediction for the whole county and never determines whether a particular home should be tested. EPA recommends testing every home regardless of zone.

Should I test my home in Johnson County?

Yes. Testing is the only way to know the radon level in a specific building. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. How to test a home.

When is the best time of year to test?

EPA says short-term tests stay in the home from 2 to 90 days and that all radon tests should run a minimum of 48 hours; long-term tests stay more than 90 days. EPA's guides do not name a best season: they say radon levels tend to vary from day to day and season to season, so a long-term test is more likely than a short-term test to tell you the year-round average.

What does it cost to test?

EPA's Citizen's Guide calls testing easy and inexpensive, and EPA's Home Buyer's and Seller's Guide says passive short-term and long-term devices are generally inexpensive, while active devices may cost more. No national average price is published for this, so Radon411 does not give one. What testing costs.

Which counties border Johnson County?

Johnson County borders 7 counties, derived from Census county geometry. Radon potential follows geology rather than county lines, so a bordering county's report can be relevant.

What these figures mean if you own, buy, sell or rent

The reported-test figures on this page describe Johnson County, Tennessee in 2023. They describe tests other people carried out in other buildings, and none of them measures yours.

  • If you own your home

    Test the lowest lived-in level; a short-term kit screens in days, a long-term kit reflects the year.

    How to test a home
  • If you are buying

    Ask for past results and any system's post-mitigation test, and test during the sale.

    Buying a house: radon guide
  • If you are selling

    Testing before you list puts the timing in your hands; disclosure rules differ by state.

    Selling a house: radon guide
  • If you rent, or rent out a home

    A tenant can test; a fix is the owner's to make, and duties differ by state.

    Radon in rental homes

How long a test has to run, under what conditions, and what EPA says a result means: the testing standard, in full.

Johnson County, Products

Testing and mitigation products

Whatever the figures for Johnson County show, only a test tells you about one home.

Johnson County / Next steps

What to do next

Informational. Follow EPA guidance. EPA says all radon tests should be taken for a minimum of 48 hours, with windows and doors closed from 12 hours before a short-term test.