Learn
Radon and real estate — what disclosure laws and home tests actually require
If you're buying a home, radon is one of the lowest-friction risks to address. Most states have specific disclosure laws, at-home tests are cheap, and remediation is well-understood. Here's what you need to know.
Published 2026-04-25 · Last reviewed 2026-05-13 · methodology
Disclosure laws by state
Required disclosure (positive duty): IL, MN, NJ, RI, FL, MA. Sellers must disclose any known radon test results or mitigation systems.
Recommended disclosure: most other states recommend (via real-estate forms) but don't legally require disclosure.
Implied caveat-emptor: a few states give buyers the right to test pre-closing but don't require disclosure.
If you're buying in a high-radon (Zone 1) county, even where disclosure isn't required, ask the seller in writing.
Pre-purchase testing
Short-term test (2–7 days, ~$15–30): typical pre-closing test. Buyers usually order it via the home inspection.
Test placement: lowest livable level (basement if finished, ground floor otherwise). Closed-house conditions for 12+ hours before/during test.
Threshold: EPA action level is 4 pCi/L. Above that, request mitigation as a contingency or seller credit.
How to interpret an installed mitigation system
Look for: PVC pipe running from sub-slab to the roof, with an inline fan box (usually attic or exterior). 'Active soil depressurization' is the standard.
Cost to install new: $800–$2,500. Cost to maintain: ~$5–15/year electric for the fan, fan replacement every 5–10 years.
If the seller has a system installed, ask for: the post-mitigation test results, the contractor's invoice, and the system's age.
What zipradar shows
EPA Radon Zone (1/2/3) for the county. Plain-English risk classification.
We do not show address-level radon levels — those don't exist as a published dataset. At-home testing is the only address-level measurement.
Related zipradar topics
Glossary terms used here
More from /learn/
- Flood zones explained — what AE, X, and VE actually mean
- EPA Radon Zones — what 1, 2, and 3 mean and when you should test
- FBI UCR and NIBRS — what crime statistics actually show (and don't)
- Lead and Copper Rule 2024 — the federal lead-pipe inventory mandate
- Property tax millage — what 'mill' means and how your bill is computed
- AQI explained — what 50, 100, 150 actually mean for your lungs
- School district boundaries — how to confirm yours and why it matters
- Wildfire Hazard Potential — what the USFS scale means and how to defend your home
- EPA SDWIS — how to read drinking-water violations and what they actually mean
- Deed records — what they show and what they don't
- Zoning codes — what R-1, C-2, M-1, MU mean and why your house is one
- Homestead exemption — state-by-state property tax savings
- Reading FBI UCR national crime trends — what 2020–2025 actually shows
- AirNow + wildfire smoke — when AQI is a real-time tool
- Wildfire insurance in 2026 — why premiums spiked and what to do
- NCES Common Core of Data — what district boundaries actually mean for buyers
- EPA SDWIS — reading drinking-water violations without panicking
- FEMA flood zones — AE vs. X vs. VE in plain English
- County assessor data — how millage rates and assessments actually combine
- NSOPW — why zipradar deep-links instead of caching the registry
- FEMA LOMA — when your home is wrongly in a flood zone (and how to appeal)
- NCES SABS — the only authoritative US school attendance map
- Deed activity by ZIP — what aggregated transfers tell you about market trends
- Buying a house — the 12-dimension data checklist before you sign
- Private well water — what to test when EPA SDWIS doesn't cover you
- County recorder vs. county assessor — they sound the same, they're not
- Zoning overlays — historic, flood, environmental layers that change what you can build
- PFAS in drinking water — what 2024's new MCLs actually mean
- Lead in paint vs. lead in pipes — same metal, different exposure
- EPA Superfund + Brownfields — what 'contaminated site nearby' actually means
- Property tax escrow — why your monthly payment changes after you close
- AQI thresholds — what 'unhealthy for sensitive groups' actually means for you
- HOA + deed restrictions vs. zoning — three regimes that govern what you can do
- Data staleness — when to re-check zipradar before making a decision
- EPA AirNow — when to watch for particulates vs. ozone
- USGS earthquake hazard maps — when separate earthquake insurance is worth it
- Septic systems — what they fail on, what tests cost, when they're a deal-breaker
- Title insurance — what it actually covers, why it's a one-time premium, and why you can't skip it
- Closing day — what actually happens + the documents you'll sign
- Radon disclosure during real-estate transactions — state-by-state
- Mello-Roos + special tax districts — the property-tax extras you didn't see
- Groundwater vs municipal water — which does your address have, and how to tell
- Defensible space zones 0/1/2 — California's 100-foot rule + what works in practice
- Base Flood Elevation (BFE) — the number that decides flood insurance
- Tornado risk by region — wind zones, safe rooms, and roof rating
- Hurricane evacuation zones and storm-surge maps — what the colors mean
- Drought, water rights, and private wells — when your tap runs dry
- FCC broadband data — checking real internet speed before you buy
- EV charging access by ZIP — DOE AFDC data + home Level-2 install
- Walk Score, Bike Score, Transit Score — what they actually measure
- Noise pollution maps — airports, highways, freight rail by address
- First-time homebuyer programs — federal + state + local stack
- Abandoned property + tax sales — buying via county auction
- Extreme heat days + cooling equity — climate risk by ZIP
- Permit history + unpermitted work — what to verify before close
- Fixed-rate vs ARM — which mortgage type fits when
- Closing costs explained — what the buyer typically pays
- Earnest money — how much, when refundable, where it goes
- FHA vs conventional — when each loan makes sense in 2026