Radon and Your Illinois Home Sale: What Sellers Must Hand Over and What Buyers Should Test

Radon is one of those words that makes buyers and sellers tense up the moment it shows up on a form. It doesn't have to. In Illinois, radon is a normal part of almost every home sale, and once you know what the law asks for and how testing works, it becomes just another item on the checklist.

Here's the plain-English version I walk my own clients through.

What Illinois requires from sellers

Under the Illinois Radon Awareness Act, the seller of residential property has to give the buyer two things before the buyer is obligated under a contract: the state's pamphlet called "Radon Testing Guidelines for Real Estate Transactions" and the Illinois Disclosure of Information on Radon Hazards form. (420 ILCS 46/10)

On that form, the seller initials what applies: that elevated radon is known to be present, that records have been provided, that the seller has no knowledge of elevated radon (or it was mitigated), or that the seller has no records. The seller also has to share any radon test results in their possession that show elevated levels.

If the disclosure happens after a buyer has already made an offer, the law says the seller has to finish the disclosure before accepting that offer and give the buyer a chance to review it and possibly amend the offer. That's why I get the radon paperwork ready before a listing goes live.

Radon also appears on the standard Residential Real Property Disclosure Report that Illinois sellers fill out. Item 15 asks whether the seller is aware of unsafe concentrations of radon on the premises. (765 ILCS 77/35)

What the law doesn't require

Here's the part that surprises people: neither law requires the seller to test for radon or to fix it. The Radon Awareness Act says so directly. The disclosure is about what the seller knows, not about running new tests.

That said, the state's pamphlet notes that many lenders, relocation companies and buyers ask for a radon test anyway, and it cautions sellers and brokers to err on the side of full disclosure. (IEMA radon pamphlet, PDF)

How a real estate radon test works

The Illinois Emergency Management Agency strongly recommends that all homebuyers test before buying or moving in, and that the home be mitigated if elevated levels are found. It also recommends hiring a licensed radon measurement professional rather than relying on someone else's test. (IEMA real estate radon page)

According to the state's real estate testing guidelines:

• The test goes in each of the lowest areas you could live in, such as a finished basement, family room or bedroom, even if that space isn't being used right now. If a home has a basement plus a slab or crawl space section, each area gets its own test.
• Testers avoid kitchens, laundry rooms and bathrooms, and don't place detectors in crawl spaces or right next to a sump pump.
• A real estate test is typically either two detectors running side by side for 48 hours or longer, or one continuous monitor that records hourly for 48 hours or longer.
• The recommendation is to fix the home if the result is 4 pCi/L (picocuries per liter) or more in any of those lowest areas.

Sellers: here's how to make the test go smoothly

Most short tests require "closed-house conditions." That means keeping windows closed and doors shut except for normal coming and going, starting at least 12 hours before the test and lasting the whole test. Heating and cooling run normally. Fans that pull in outside air stay off.

The good news is that fall and winter in Chicagoland make this easy, since the windows are already shut. A few practical tips:

• Leave the detector alone. Under the state's guidelines, interfering with a radon measurement is illegal in Illinois.
• Tell anyone showing the home to keep doors closed. Licensed testers post a notice at every entry.
• If you already have a mitigation system, gather the paperwork and any past test results now, and make sure the fan is running.

Buyers: what to do if the number comes back high

A high result doesn't mean you have to walk away. The state's own disclosure form says elevated radon can easily be reduced by a qualified, licensed radon mitigator. After a system goes in, IEMA recommends an independent short-term test to confirm it's working.

In practice, a high reading usually becomes a negotiation during attorney review or the inspection period: a repair, a credit or a price adjustment. Your attorney handles the contract language, and I keep everyone moving toward closing.

The bottom line

Radon is a paperwork-and-testing item, not a deal-breaker. Sellers who prepare the disclosure early avoid last-minute delays. Buyers who test with a licensed pro go into closing knowing exactly what they're getting.

If you're buying or selling anywhere in Chicago or the suburbs, call or text me at 312.882.9797. I'll make sure the radon piece, and everything else, is handled right. Full-service real estate, lower commission.

This article is general information, not legal or health advice. For questions about a specific contract, talk with a real estate attorney, and for testing or mitigation, use an Illinois-licensed radon professional.