01.2
pCi/L maximum · Knox County
The Tennessee Radon Testing dashboard returned this maximum on two separate, county-label-verified reads.
The headline
A radon-ready home is not the same as a radon-safe home.
Knox County sits in the EPA's highest-potential radon zone. Building codes can create a useful path for soil gas, but only a test tells you what is in the air—and the code now changes at the Knoxville city limit.
The jurisdiction line
Same county. Different requirement.
Choose the jurisdiction for the concise rule. Municipal boundaries—not the mailing address alone—control which code applies.
Radon-resistant construction is no longer code-required.
- Current code2024 IRC
- EffectiveJanuary 1, 2025
- AuthorityEmergency Ordinance O-125-2024
- Appendix listBA, BB, BC, BD, BF, BI, BJ, BK, BL, BM and BN—not BE, the 2024 radon appendix.
A passive radon system remains part of new one- and two-family construction.
- Current evidence2018 IRC
- EffectiveJanuary 1, 2019
- AuthorityOrdinance O-18-10-101
- Appendix listA, B, C, D, E, F (Radon Control Methods), G, H, J, K, M, N, O, P and Q.
Sources: Knoxville O-125-2024, Knox County 2018 IRC amendments, and county code-adoption history.
What the measured data says
The verified number is the maximum—not an average.
Source: Tennessee Radon Testing dashboard, checked October 16, 2026. Its period covers 2022–2023 and its county average/median fields did not render for Knox.
A practical plan
Treat the pipe as infrastructure. Treat the test as evidence.
Test the occupied space
New, old, city, county, basement or slab: a code label cannot substitute for a radon measurement.
Inspect the system
Look for a labeled vertical pipe, sealed penetrations and a fan rough-in. Ask whether the pipe terminates capped in the attic.
Activate if needed
A passive system can often accept a fan. Confirm the installed system and retest after any mitigation work.
110V
RADON PIPE
What the county handout calls for
Unincorporated Knox County's prescriptive guidance describes a 3–4 inch tee in at least 4 inches of gravel, sealed slab penetrations, a vertical vent to the attic, labels at each floor and in the attic, and a 110V outlet for a future fan.
A capped attic pipe is a passive system—not proof that the home's radon level is low.
Read the county construction handoutBuying and selling
Radon is on the disclosure form. Testing still belongs in the contract.
- Buyers: keep the contingency.The form itself advises buyers to include a radon inspection contingency. A seller does not have to test before completing the disclosure.
- New builds deserve extra scrutiny.New construction with a written warranty can be exempt from the disclosure form. Do not treat “new” as “tested.”
- Ask which jurisdiction issued the permit.City homes permitted under the 2024 IRC may have no passive rough-in; unincorporated county homes should be checked against the county's Appendix F requirements.
- Multifamily is a separate concern.Of 5,822 housing units permitted in 2025, 3,519 were multiunit. Those homes fall outside the one- and two-family IRC framework discussed above.
Sources: TAR Form RF201 and Knox Planning 2025 Development Activity Report.
Finding a professional
There is local capacity—but much of it is bundled with home inspection.
NRPP provider listings with Knoxville or Knox County addresses
This is an address-based count across provider types. The directory's measurement-only filter did not isolate cleanly, so it is not an exact count of measurement specialists.
NRSB measurement specialists within 25 miles of 37902
One was listed in Knoxville and one in Oak Ridge. The same search returned zero measurement technicians.
Questions people ask
Knox County radon FAQ
Is radon-resistant construction required in Knoxville?
No. Knoxville's 2024 IRC adoption, effective January 1, 2025, omits Appendix BE for Radon Control Methods. The city included the radon appendix under its 2012 and 2018 code editions.
Is it required in unincorporated Knox County?
The county's 2018 IRC adoption specifically includes Appendix F, and its Code Administration office publishes a prescriptive passive-system handout. The available evidence indicates the requirement applies to new one- and two-family homes. For a project-specific determination, ask the county to confirm the ordinance's designation language.
Does a radon pipe mean my home is safe?
No. The pipe is a pathway for soil gas; a passive pipe or capped attic rough-in is not a measurement and may not include an operating fan. Test the home, then determine whether activation or other mitigation is needed.
Are there special local rules for schools or public buildings?
No Knox County- or Knoxville-specific rule was found in the reviewed web sources. Tennessee is described as encouraging, rather than requiring, school testing. A direct check with local health and code offices would close this open question.
Primary references
Source file
- City of Knoxville Emergency Ordinance O-125-2024
- City of Knoxville current codes
- 2024 IRC Appendix BE: Radon Control Methods
- Knox County 2018 IRC amendments
- Knox County radon construction handout
- Knox County code adoption history
- EPA Map of Radon Zones
- Tennessee Radon Testing dashboard
- Tennessee Residential Property Condition Disclosure (RF201)
- Knox Planning 2025 Development Activity Report
- NRPP professional search
- NRSB Find a Professional