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Radon disclosure during real-estate transactions — state-by-state
Radon is the second-leading cause of lung cancer in the US (after smoking). But seller-disclosure rules are wildly inconsistent across states. Here's what's actually required where you're buying.
Published 2026-04-25 · Last reviewed 2026-04-26 · methodology
Mandatory-disclosure states (sellers MUST disclose known radon results)
Illinois — IL Public Act 095-0210 requires sellers to provide a Radon Disclosure form before contract.
New Jersey — Radon Hazard Disclosure required by NJ statute on every residential resale.
Florida — radon notice required in every real-estate contract; doesn't require testing, only the disclosure language.
Several others (RI, IA, MN, etc.) have variant rules. Always check your state's real-estate-commission disclosure form.
States with no mandatory disclosure
About half the country. Sellers may legally not mention prior radon test results even if they had elevated readings.
Common-law fraud rules still apply: a seller who actively conceals (paints over a radon-mitigation system pipe) can be sued post-closing. But passive non-disclosure in non-mandatory states is generally legal.
What to ask for during inspection
Add a radon test contingency. Cost: $25-150 for a 48-hour short-term test. Some inspectors include it; many add it as a la carte.
If radon was previously tested, ask the seller for the test reports (date, location of test, result in pCi/L).
If a mitigation system is installed, ask: when was it installed, by whom, has it been re-tested since, where's the system maintenance log.
EPA action level: 4.0 pCi/L. WHO recommends 2.7 pCi/L. The lower the better; mitigation is straightforward and affordable ($800-2,500 for active sub-slab depressurization).
What zipradar shows
EPA Radon Zone classification (1-3) per ZIP code — the regional risk indicator. See /topic/radon/[zip]/.
Zone 1 = highest predicted potential (>4 pCi/L average indoor); Zone 2 = moderate (2-4 pCi/L); Zone 3 = low (<2 pCi/L).
Zone classification is regional + advisory, NOT a substitute for testing your specific home. Side-by-side homes can have very different radon levels.
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