The bottom line
The county color is not a home test.
EPA’s Zone 3 label predicts a countywide average below 2 pCi/L. Marion County’s state dashboard tooltip told a different story: 5.2 average, 4.6 median, and 10.2 maximum. All three values were reproduced twice with the tooltip explicitly labeled “County: Marion.” Test every home—including new construction.
A “low-potential” label meets an above-action average.
EPA’s zone map is a planning tool based on broad geology and predicted screening levels. The Tennessee dashboard is a test snapshot. Neither can tell you the level in a specific house, but together they show why the zone cannot be used as a pass.
predicted average <2 pCi/L
Marion, Grundy, and Franklin counties are listed in Zone 3. Hamilton County is Zone 2. Elevated homes can still occur in any zone.
EPA Map of Radon Zones ↗ · EPA Map of Radon Zones: Tennessee
Two consecutive live reads returned the same three values and the label “County: Marion.” The Year filter was “(All),” covering 2022–2023. The tooltip showed no test count, so these figures cannot establish how common elevated homes are across the county.
Source: Tennessee Radon Testing dashboard, checked October 16, 2026. The pre- and post-mitigation band charts are health-region aggregates, not Marion County counts; none are presented here as county figures.
Local code records show no verified radon guarantee.
Unincorporated Marion County and four municipalities use different IRC editions or enforcement paths. Only Monteagle’s published record names an appendix—and it names Appendix Q, not the radon appendix. The State Fire Marshal card explains the fallback program rather than a sixth local jurisdiction.
2018 IRC · effective January 1, 2020
The county’s April 1, 2026 permit guide lists eight adopted base codes, including the 2018 IRC. It does not publish an appendix schedule or the adopting resolution number.
Radon status: Appendix F not verifiable; radon-resistant construction is not confirmed mandatory.
Current IRC edition not verified
The online municipal code copy is stale, while Jasper’s 2024 zoning ordinance identifies a building-inspector role. No current residential-code adoption was found.
Radon status: unknown. If Jasper does not operate its own program, State Fire Marshal residential standards may apply.
2012 IRC · Ord. #776, July 2017
The retrieved Title 12 record shows the 2012 IRC and selected local modifications, but no appendix schedule was visible.
Radon status: Appendix F not shown as adopted; requirement not confirmed.
2015 IRC · Ord. #331, January 2017
Whitwell adopted the 2015 IRC with subsequent amendments and deleted the automatic-sprinkler section. No appendix schedule is listed.
Radon status: radon appendix not shown as adopted; requirement not confirmed.
2018 IRC · Ord. #13-21, August 2021
Monteagle’s current record names only Appendix Q as adopted.
Radon status: Appendix F is not adopted; radon-resistant construction is not mandated by Monteagle’s code.
2021 ICC codes · effective April 17, 2025
The state enforces residential standards where a jurisdiction does not adequately run its own program. Marion County’s own program covers unincorporated areas; Jasper’s status remains the local open question.
No Marion County jurisdiction was verified to require the applicable IRC radon appendix. Ask the builder for plans or installation evidence, then test the completed home rather than assuming “built to code” means radon-ready.
No county-specific radon mandate was found.
The indexed county and municipal records produced no special Marion County rule for public buildings, schools, or residential transactions.
Testing still enters through due diligence.
The Tennessee disclosure regime does not force a seller to perform a radon test. Buyers can include radon in their inspection contingency and order testing during the due-diligence period.
Tennessee policy encourages school testing rather than requiring it in the material reviewed. A 2018 bill that would have added radon testing to annual school indoor-air evaluations was found, but its enactment was not verified. TDEC provides technical help for schools and free test kits for Tennessee homeowners.
Tennessee disclosure form ↗ · School-policy review ↗ · Request a TDEC test kit ↗
How do I find a certified radon professional in Marion 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.
Make radon part of the deal—not an afterthought.
Marion County’s mix of established homes and new communities makes the same rule useful across the market: preserve time to test, and do not assume a new build includes radon controls.
Keep a radon contingency
Order the test inside the inspection or due-diligence window; Tennessee does not require the seller to test first.
Test new homes too
No local jurisdiction was verified to mandate the radon appendix, even where a current IRC edition is enforced.
Verify the professional
Local certified supply is thin. Check current NRPP or NRSB credentials rather than relying only on a service label.
Retest after mitigation
A completed system should be followed by a new measurement to confirm that levels were reduced.
Angi’s Whitwell guide gives this local-market range; actual cost depends on the house and system design. An East Tennessee specialist reports typical reductions of 80–99%, but the finished system still needs a confirming retest. Whitwell cost context ↗ · East Tennessee transaction guide ↗
Codes, public data, and live directories.
Sources were reviewed for Marion County on October 16, 2026. Live directory and dashboard values are dated snapshots.
- Marion County — Building permit requirements
- MTAS — South Pittsburg Title 12
- MTAS — Whitwell Title 12
- MTAS — Monteagle Title 12
- MTAS — Jasper municipal code copy
- Jasper zoning ordinance, 2024
- MTAS — local code adoption explainer
- AIA Tennessee — State Fire Marshal code update
- Tennessee Radon Testing dashboard
- EPA Map of Radon Zones
- EPA Map of Radon Zones: Tennessee
- NRPP Find a Professional
- NRSB Find a Professional
- Tennessee property-condition disclosure
- HB1269 school IAQ bill text
- 50-state school radon policy review
- TDEC homeowner radon test-kit request
- Jasper Gulch announcement
- Homes.com — Marion County new construction
- Angi — Whitwell radon services and cost context
- RN86 Solutions — East Tennessee home sales guide
Dashboard tooltip values are a 2022–2023 snapshot and do not include a county test count. Health-region charts are not county data. Professional-directory listings are opt-in and may change. Code status is stated only to the level supported by the published records.