EPA radon zone
1
High potential: predicted average indoor screening levels above 4 pCi/L.
01 / RISK SIGNAL
The zone map and the dashboard answer different questions.
EPA Zone 1 predicts countywide radon potential. Tennessee’s dashboard summarizes a small, voluntary 2022–2023 test sample. A lower observed average does not cancel the geological risk classification.
Sources: 2018 IRC Appendix F Zone 1 table · Tennessee Radon Testing dashboard2.0
pCi/L · DASHBOARD AVERAGE
2 of 4 readsshowed the average; the first two reads loaded that field blank.
2.9pCi/L · maximum · confirmed on all four reads
Not verifiedMedian · blank on all four reads
Read the limits with the numbers. The county label was verified on every live tooltip read. The dashboard does not expose a Smith County test count, and its pre/post charts switch to the Upper Cumberland Region—not county data. The earlier 1.2 median transcription is withheld.
02 / CODE SPLIT
The county answer is clear. Three town records remain incomplete.
Choose a jurisdiction to see the strongest published record. “Open” means the current ordinance or appendix list could not be verified online—not that the radon appendix is definitely absent.
Unincorporated Smith County
State residential permit and inspection program
Residential code2018 IRC
Adopted appendixAppendix Q only
Radon appendixAppendix F not adopted
Smith County has no county-adopted residential building code. The State Fire Marshal requires a state residential permit in unincorporated areas and applies Tennessee’s 2018 IRC standard. Rule 0780-02-23-.02 names Appendix Q—not Appendix F—so radon-resistant new construction is optional. The exact effective date of the 2018 update was not pinned down.
SFMO permit jurisdiction list · Tennessee rulemaking filingCarthage
Current town page confirms several 2018 I-Codes, but not the IRC
Town page2018 Building, Plumbing, Mechanical & Fire Codes
Current IRC editionNot verified
Appendix FNot verified
The town’s live Building Permit page does not name the residential code edition or a radon appendix, and its Codes & Ordinances page posts no building-code adoption ordinance. Under 2018 IRC §R102.5, an appendix applies only when the adopting ordinance specifically references it.
Town of Carthage Building Permit page · Codes & OrdinancesSouth Carthage
Only a dated municipal codification was located
Published housing code1997 Standard Housing Code
Published ordinanceOrd. #123 · November 1989
Current editionNot verified
The MTAS copy is a July 1999 codification updated through January 2003. It may not reflect current practice and cannot establish a modern radon appendix.
MTAS South Carthage codeGordonsville
Published Title 12 is dated November 2011
Published residential code2009 IRC
Published section§12-401
Appendix listNone published
The online code names the 2009 IRC but does not publish an appendix list or radon provision. No later update was found, so whether this edition remains current is open.
MTAS Gordonsville Title 12What can be said countywide
Radon-resistant new construction is not required in unincorporated Smith County. No published requirement was found in Carthage, South Carthage or Gordonsville, but the towns’ current appendix status remains unverified and should not be presented as a final legal conclusion.
How do I find a certified radon professional in Smith 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.
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 / HOMEBUYERS
Growth is adding homes without a radon construction mandate.
Smith County sits between the Nashville metro and the Upper Cumberland. Every transaction—and especially every new build—deserves a test rather than an assumption based on age or code compliance.
Source: U.S. Census Bureau QuickFacts · Smith County20,981
Population estimate for July 1, 2025.
+5.4%
Population change since April 2020.
153
Building permits reported for 2025.
Put radon in the inspection contingency.
Tennessee disclosure covers hazards the seller already knows. A test creates new information before the contract becomes final.
Test a new build.
Unincorporated construction follows the 2018 IRC without Appendix F. A written warranty may also exempt new construction from the state disclosure form.
Do not use 2.0 as an address-level prediction.
The dashboard value comes from a small voluntary sample with no published county test count.
Use a nationally certified provider—or begin with TDEC.
NRPP and NRSB directories show credentialed providers; Tennessee’s Radon Program offers free homeowner test kits.
04 / TESTING RESOURCES
Radon testing resources
Start with a home test, then use qualified guidance if the result is elevated. These national hotlines are supported by EPA and CDC.
Test your home
- Free test kit from TDECRequest a kit from Tennessee’s radon program
- Buy a kit by phone1-800-SOS-RADON (1-800-767-7236)
- Live help with your questions1-800-55RADON (1-800-557-2366)
- Find a certified proNRPP 800-269-4174 · NRSB 866-329-3474
If your result comes back high
1-800-644-6999 — the Fix-It Hotline, for general guidance on lowering radon in your home.
Learn more
05 / LOCAL & STATE RULES
No Smith County-specific radon rule was found.
Published county and municipal records did not surface a radon rule for public buildings, schools or real-estate transactions. Tennessee’s statewide baseline remains limited.
Testing is encouraged, not required.
TCA §49-2-121 says an LEA’s inspection program may include radon testing. It creates no statewide mandate or retest interval. Source
Known hazards must be disclosed.
The statewide disclosure framework includes known radon but does not require the seller to test. Exemptions and a disclaimer route may apply. Source summary
No local survey rule located.
No Smith County equivalent to Metro Nashville’s recurring public-building radon survey regulation was found in published records.
06 / SOURCES & METHOD
A dated evidence trail, with the gaps left visible.
Live dashboard and directory observations were checked October 15, 2026. Other claims rely on the linked state, federal, municipal, legal and census records. No health-region chart was treated as Smith County data.
The dashboard’s county tooltip does not say whether average and maximum combine pre- and post-mitigation tests. Its missing sample size prevents a prevalence estimate. Provider directories are self-reported and can omit active testers.
Code conclusions distinguish a confirmed adoption from an inference based on a dated or incomplete public record. This is research, not legal advice.
- Tennessee Radon Testing dashboard
- EPA radon zone maps
- 2018 IRC Appendix F
- SFMO Residential Permits
- SFMO permit jurisdiction list
- Tennessee Rule 0780-02-23 filing
- Town of Carthage Building Permit
- Carthage Codes & Ordinances
- Smith County Planning Office
- Smith County Development Guide
- MTAS South Carthage code
- MTAS Gordonsville Title 12
- 2018 IRC §R102.5
- NRPP professional directory
- NRSB professional directory
- TCA §49-2-121
- Environmental Law Institute
- Census QuickFacts · Smith County
- TDEC Radon Program
- American Lung Association · Radon