Radon and real estate — what disclosure laws and home tests actually require

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.