Illinois Radon Disclosure Requirements for Sellers (2026)

Illinois is one of the few states that specifically requires radon disclosure in real estate transactions. Here's what Chicago-area FSBO sellers need to know.

What Illinois Law Requires

Under the Illinois Radon Awareness Act, home sellers must:

Provide the IEMA radon pamphlet — "Radon: A Guide for Illinois Homebuyers and Sellers" — to buyers before contract execution

Disclose known radon test results on the Illinois Residential Real Property Disclosure form

Disclose any radon mitigation systems on the property

Do You Have to Test?

No. Illinois does not require sellers to test for radon. However:

If you have tested, you must disclose the results

Buyers frequently request radon tests as a contingency

If you haven't tested, buyers may request testing during the inspection period

What If Radon Levels Are Elevated?

The EPA action level is 4 picocuries per liter (pCi/L). If your test result is above 4 pCi/L:

You must disclose this result

You are not required to mitigate before selling

Buyers will likely negotiate — either a price reduction or a seller-installed mitigation system

Mitigation systems typically cost $800–$2,500 and are highly effective

Why Radon Matters in Chicago

Illinois has elevated radon risk compared to the national average due to underlying geology. The Chicago area has pockets of both low and high radon levels. Testing costs $15–$30 for a DIY kit from Home Depot, or $100–$200 for a professional test.

Disclosing proactively — or having a recent test on hand — builds buyer confidence and reduces negotiation friction.

Download the Illinois Radon Disclosure form free on our Disclosures page.

Illinois Radon Disclosure Requirements for Home Sellers (2026)

Illinois Radon Disclosure Requirements for Sellers (2026)

What Illinois Law Requires

Do You Have to Test?

What If Radon Levels Are Elevated?

Why Radon Matters in Chicago

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