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Radon Zones and Property Screening

A county zone can help frame environmental follow-up, but only a building test can establish that building's indoor radon level. EPA recommends testing homes in every zone.

Practical guide

Buyers, agents and property reviewers organizing indoor-environmental due diligence.

By TrueViewly. Last reviewed:

What the county zone contributes

EPA's 1993 map groups counties by potential indoor radon levels. Zone 1 has the highest potential, Zone 2 moderate potential and Zone 3 lower potential. These are regional categories, not measurements of the property.

  • The date of a downloaded data file is not the date of the underlying model.
  • A lower-potential zone is not a guarantee of a low indoor concentration.

How TrueViewly matches the location

The report requires a unique intersecting county polygon and an exact validated county-FIPS match to the prepared EPA crosswalk. Historical or changed county geographies without a validated match remain unresolved; the runtime does not guess a zone.

  • The panel records county, zone and source context where matched.
  • Territories have no coverage in this imported radon table; source availability must be read separately from risk.
  • The county panel does not change the existing environmental or overall risk score.

Follow up with building evidence

Arrange testing appropriate to the building and transaction. Discuss existing results, mitigation records and any retesting needs with a qualified testing or mitigation professional.

  • Do not use the county zone to waive a test.
  • For detailed testing and mitigation guidance, consult EPA and the applicable state or local program.
  • Keep regional context, actual test results and professional recommendations clearly separated.

Sources and further reading

Source publications and live agency pages may differ from the snapshot used in a report. Check the report's source dates and confirm material findings through the responsible authority.

Frequently asked questions

Can a Zone 3 property have elevated radon?

Yes. Elevated indoor levels can occur in every zone; a building test is the relevant next step.

Is this report a radon test result?

No. It shows a historical county category, not indoor concentration.

Does no county match mean there is no radon concern?

No. It means the source could not be reliably matched and does not remove the need for testing.

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TrueViewly reports are informational decision-support outputs based on available datasets and user-provided inputs. They are not certifications, legal advice, engineering opinions, insurance determinations, government approvals, or a replacement for official records and professional due diligence.

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