Tennessee Radon Authority
Updated October 17, 2026
CLAY COUNTY RADON · TENNESSEEResearch verified Oct. 16, 2026

Clay County, TN radon Low-zone label.
Outside Celina, no code safety net.

Unincorporated Clay County opted out of residential building codes. The state map calls the county Zone 3, yet the state testing dashboard shows a 2.5 pCi/L average. The practical conclusion is simple: every home still needs a test.

Illustrated cutaway of a rural lakeside Tennessee home above limestone and shale, with radon rising toward the foundation and a test device below grade
Radon moves from soil and rock into buildings through foundation openings. Illustration is explanatory, not a map or site-specific model.

Radon in Clay County, Tennessee: quick answers

EPA zone: Zone 3Region: Middle TennesseeState test data: State test figures seen once; shown with a caveat

Is radon a problem in Clay County, Tennessee?

It can be. Clay County is in EPA Zone 3, the lowest predicted radon-potential category (below 2 pCi/L on average). Homes with high radon are still found in Zone 3, and the Tennessee Radon Program has found homes needing action in every Tennessee county, so test to know your home's level.

Do new homes in Clay County, TN have to be built radon-resistant?

No, not outside Celina: unincorporated Clay County opted out of residential codes effective August 10, 2026, so no building code applies. Celina's current code couldn't be confirmed. Local code details

How do I test my home for radon in Clay County?

Order a free short-term kit from the Tennessee Radon Program online or by calling 1-800-232-1139. Place it on the lowest lived-in floor, about 3 feet off the floor, for 3 to 5 days, then mail it back right away. How to test your home

What radon level means I should fix my home?

EPA recommends fixing your home if radon is 4 pCi/L or higher, and considering a fix between 2 and 4 pCi/L. Confirm a high short-term result with a second test first. What your result means

Who can test or fix radon in Clay County?

Tennessee doesn't license radon professionals, so look for NRPP or NRSB certification. Search both national directories by ZIP code; certified professionals often serve Clay County from nearby cities. How to choose a radon professional

2.5pCi/L dashboard average · single clean read
Zone 3EPA predicted average below 2
0NRPP or NRSB pros based locally
Aug. 102026 county opt-out date
01 / BUILDING CODES

No mandate outside Celina.

The jurisdiction split is unusually stark: a confirmed unincorporated-county opt-out, an unresolved city record, and no radon appendix in Tennessee's state program.

Outside Celina, the answer is settled: unincorporated Clay County has no residential building code in force. The commission's two-thirds vote ended local standards for one- and two-family dwellings and mobile homes outside municipal limits.[1]

Unincorporated county

Confirmed opt-out

IRC edition: none.
Radon appendix: none.
Radon-resistant construction: not required.
Effective: August 10, 2026. The resolution number was not published.

City of Celina

Open question

Celina does not appear on the State Fire Marshal's live state-permit list, but no local adopting ordinance or opt-out resolution was found. Its current IRC edition and radon-appendix status remain unverified.[2]

Where the State Fire Marshal does enforce residential standards, Tennessee uses the 2018 IRC with Appendix Q only. Appendix F—the 2018 radon-control appendix—is not included. State enforcement therefore does not create a radon-resistant construction mandate.[3]

A newly built home in Clay County should not be assumed “radon-ready.” Ask what was installed, inspect the feature, and test after occupancy.Practical implication of the verified code record

No Clay County– or Celina-specific radon rule was found for public buildings, schools, or real-estate transactions. Tennessee encourages school indoor-air programs but does not impose a home-testing mandate or license radon professionals at the state level.[4]

02 / RISK PROFILE

A low-potential zone is not a pass.

EPA zones predict county-scale potential. They cannot tell you the level in a particular house.

EPA classifies Clay County as Zone 3, defined as predicted average indoor radon below 2 pCi/L.[5] But the Tennessee dashboard's county tooltip shows a higher observed average for 2022–2023 tests.

Observed county average

<22–4>4 pCi/L

2.5 pCi/L falls in the dashboard's “Between 2 to 4” band.

2.5Average pCi/L · published with caution
—Median withheld
—Maximum withheld
Read with care. One clean, label-confirmed “County: Clay” tooltip read rendered 2.5 average, 1.1 median, and 2.6 maximum. Those three figures cannot describe one ordinary distribution—the average could not sit that close to the maximum while at least half the values are at or below 1.1—so this page withholds the median and maximum pending underlying data. The 2.5 average is shown only as the dashboard's rendered value, not as a fully reconciled county statistic. Multiple repeat attempts landed on neighboring counties because Clay's map polygon is small. The prior 1.9 / 1.2 / 2.7 transcription was incorrect and is not used here. The dashboard does not publish the county sample size.[6]

The dashboard's pre- and post-mitigation band charts are Upper Cumberland Region aggregates, not Clay County counts. They should not be used to report a Clay County test count or percent above 4 pCi/L. EPA itself cautions that its zone map is for targeting resources and building-code decisions—not deciding whether an individual home needs testing.[5]

How do I find a certified radon professional in Clay County?

Tennessee doesn't license radon testers or mitigators, so national certification is the best way to check qualifications. The Tennessee Radon Program points residents to two directories: search them by ZIP code and widen the radius if nothing is listed nearby.

Search NRPPSearch NRSB

We don't recommend or rank companies. Before you hire, check the certification number in the directory yourself and ask for a follow-up test after any system is installed. Questions to ask a radon professional.

03 / HOMEBUYER BRIEF

Make the test part of the deal.

The buyer's leverage is contractual: Tennessee's disclosure form advises a radon inspection contingency, but it does not provide a radon-specific seller checkbox.

Clay County's lake homes, older housing, rural tracts, and uninspected new construction all point to the same due-diligence step: arrange an independent test instead of relying on the EPA zone, the age of the home, or a builder's general assurances.

BEFORE OFFER

Budget the test

Ask whether any prior radon report exists, but plan for a fresh test tied to the transaction.

IN CONTRACT

Write the contingency

Tennessee's buyer advisory expressly lists radon among appropriate inspection contingencies.[9]

NEW CONSTRUCTION

Verify, then test

Ask for documentation of any radon-resistant features. With no county code mandate, installation cannot be assumed.

The area's transaction mix matters. Around Dale Hollow Lake, recreational and second-home buyers may be purchasing from a distance. Clay County's April 2026 median time on market was 116 days, according to Realtor.com, suggesting inspection contingencies may be practical in a slow-moving market.[10]

Ignore “Zone Unknown” claims on commercial lead-generation pages. EPA-based sources identify Clay County as Zone 3, while the state dashboard provides the observed 2022–2023 county values. Neither source replaces a measurement in the home itself.

04 / RADON TESTING RESOURCES

Test, understand, and act.

Official Tennessee and federal resources make the next step straightforward, whether you need a kit, live guidance, or a certified professional.

Testing is the only way to know the radon level in a home. Start with Tennessee's free kit, then use the national hotlines or credential directories when you need help interpreting or fixing a result.

Why it matters

  • Radon causes about 21,000 U.S. lung cancer deaths a year — the second-leading cause overall, and the number-one cause among people who never smoked.
  • At 4 pCi/L, EPA estimates about 62 in 1,000 smokers could get lung cancer from lifetime exposure, versus about 7 in 1,000 people who never smoked.
  • About 1 in 15 homes has high radon.
  • Retest at least every 2 years if you have a mitigation system, and after renovations or changes to how you use the lowest floor. EPA recommends taking action at 4 pCi/L and considering it between 2 and 4.[15]

Hotlines and action guidance: U.S. EPA and CDC.[14] Health statistics: American Lung Association.[16]