Radon Disclosure Requirements When Selling a Home in Illinois

Illinois Law and Radon Disclosure

Illinois requires radon disclosure under the Illinois Radon Awareness Act (410 ILCS 54). This law is more detailed than many states: it does not just require sellers to answer a question on a property disclosure form. It requires sellers to actively hand buyers a specific state-mandated document and an educational pamphlet before the contract is signed.

The Illinois Emergency Management Agency (IEMA) administers the state radon program and produces the required disclosure form and buyer pamphlet. Sellers must provide both. Failing to do so can expose a seller to civil liability if a buyer later discovers elevated radon and can show the disclosure was not made.

Illinois is classified as EPA Radon Zone 1 statewide. IEMA estimates that 40 percent or more of Illinois homes test above the EPA action level of 4 pCi/L. That figure is not evenly distributed: some parts of central Illinois see some of the highest average residential radon levels anywhere in the United States.

What the Illinois Radon Awareness Act Requires

Under 410 ILCS 54, sellers of residential real estate in Illinois must:

Provide the IEMA-approved radon disclosure document to buyers prior to or at the time of signing the purchase contract
Disclose any known radon test results, including the date, the result in pCi/L, and whether the test was conducted by a professional or a homeowner kit
Disclose any radon mitigation system on the property, including when it was installed and by whom, if known
Provide buyers with the IEMA radon educational pamphlet

The law applies to most residential sales, including single-family homes, condominiums, townhomes, and multi-unit buildings of four units or fewer.

The 96-Hour Buyer Testing Window

Illinois has a provision that is unusual compared to most states: after receiving the required disclosure form and IEMA pamphlet, buyers have 96 hours to decide whether to conduct radon testing. This 96-hour window begins when the buyer receives the disclosure materials, not when the contract is signed.

In practice, most Illinois buyers exercise this right through the standard inspection contingency period rather than relying on the 96-hour provision as a standalone mechanism. But the provision matters because it establishes that buyers have an explicit right to test and cannot be pressured by a seller or agent to skip radon evaluation.

If a buyer conducts a test during this period and the result exceeds 4 pCi/L, the buyer can negotiate with the seller for mitigation, a credit, or a price reduction. Buyers can also choose to walk away if the transaction agreement permits it under the inspection contingency.

What “Known” Means in Illinois

Like most states, Illinois requires sellers to disclose information within their personal knowledge. You are not required to test a home you have never tested. But you must disclose:

Any prior radon test results you received, regardless of how old they are
Any mitigation system on the property, whether you installed it or a previous owner did and you are aware of it
Any radon-related information disclosed to you when you purchased the home
Contractor invoices or service records related to radon work

The duty to disclose attaches to what you know, not to what a test might reveal. But Illinois courts and real estate attorneys generally advise sellers to test before listing, both to meet the spirit of the law and to take control of the transaction.

Market Context: Chicago Suburbs vs. Downstate

Chicago Metro: Cook, DuPage, Lake, Kane, McHenry, and Will Counties

Radon testing is standard practice in Chicago suburban transactions. Nearly every home inspection in the six-county collar region includes a radon test. Buyers expect it, sellers anticipate it, and agents are accustomed to negotiating around elevated results. The geology of the Chicago metro, glacial lake sediments and till deposited from the Lake Michigan basin, produces consistently elevated radon in single-family homes throughout the suburbs.

Chicago proper is a different situation. The city is dominated by high-rise and mid-rise apartment buildings and attached brick two-flats and three-flats. These building types have much higher air exchange rates than suburban single-family homes, and their concrete slab or above-grade living spaces have limited soil contact. Radon testing in Chicago proper is far less common, and the average risk in high-rises is genuinely lower. But ground-floor units in older buildings, and bungalows in Chicago's single-family neighborhoods, should be tested.

Downstate: Peoria, Springfield, Champaign, Rockford

Radon testing is increasingly common downstate, though adoption varies by market. Champaign County has some of the highest radon readings in the state, and awareness has grown accordingly. In Peoria, Springfield, and Bloomington-Normal, testing is common in transactions involving buyers who have done their research or are working with experienced agents.

The Illinois Association of Realtors has encouraged radon testing statewide, and the trend over the past decade is toward broader testing adoption outside the Chicago metro. Sellers in downstate markets should not assume that buyers will skip radon evaluation.

Post-Mitigation Disclosure: What to Include

If your home has a mitigation system installed, disclose it fully. Buyers who understand what they are looking at will view a properly documented mitigation system as a positive. Include:

The date the system was installed
The name and IEMA license number of the installing contractor
The type of system (sub-slab depressurization is the most common in Illinois)
Post-mitigation test results, including the date and result in pCi/L
Any annual or periodic re-tests conducted after installation

A mitigation system with a documented post-test showing levels below 2 pCi/L is a clean disclosure. Many buyers and their agents see it as evidence that the seller was responsible and thorough.

Seller Pre-Listing Strategy in Illinois

Testing before you list gives you information and options. If the result is below 4 pCi/L, you can include that in your disclosure package and buyers are unlikely to request a re-test. If the result is above 4 pCi/L, you can mitigate before listing and present a solved problem instead of an open question.

Mitigation in Illinois typically costs $800 to $2,500 depending on foundation type, number of suction points needed, and the contractor. That investment is almost always less than the credit or price reduction a buyer will negotiate after discovering elevated radon during inspection. Buyers in negotiation typically ask for more than mitigation actually costs, because the uncertainty of the process feels expensive to them.

A seller who can hand a buyer the IEMA disclosure form, a professional test result below 4 pCi/L (or a post-mitigation result below 2 pCi/L), and the IEMA pamphlet has done everything right. That buyer has no basis for a radon-related negotiation and is more likely to move toward closing without friction.

Illinois Radon Contractor Licensing

Illinois requires radon mitigation contractors to be licensed by IEMA. This is stricter than some states: in Illinois, you can verify that a contractor holds a valid state license before hiring them. IEMA maintains a public database of licensed radon professionals. Buyers who receive disclosure about a mitigation system can look up the contractor and verify their credentials.

When hiring for pre-listing mitigation, ask for the contractor's IEMA license number and confirm it is current. Using an unlicensed contractor may address the physical problem of elevated radon, but it may not satisfy a buyer's attorney reviewing disclosure documentation at closing.

Find a Radon Professional in Illinois

Testing and mitigation by a licensed professional protects the transaction and the health of everyone who lives in the home. Find radon professionals in Illinois licensed through IEMA and certified through NRPP or NRSB.

Frequently Asked Questions

What does the Illinois Radon Awareness Act require sellers to provide?

Sellers must provide buyers with the IEMA-approved radon disclosure form and the IEMA radon educational pamphlet before or at the time the purchase contract is signed. They must also disclose any known radon test results and any mitigation system on the property.

How long do Illinois buyers have to decide about radon testing?

Under the Illinois Radon Awareness Act, buyers have 96 hours after receiving the disclosure form and pamphlet to decide whether to conduct radon testing. In practice, most buyers exercise this right through the standard inspection contingency period.

Do Chicago high-rises need radon testing?

High-rise and elevator buildings in Chicago proper have much lower radon risk because high air exchange rates and above-grade living spaces limit soil gas infiltration. Ground-floor units in older buildings, and single-family bungalows in Chicago's residential neighborhoods, carry more risk and should be tested.

Does Illinois license radon contractors?

Yes. Illinois requires radon testing and mitigation professionals to be licensed by IEMA, the Illinois Emergency Management Agency. IEMA maintains a public database of licensed contractors. Buyers can verify contractor credentials before or after a transaction.

Is a mitigation system a red flag for Illinois buyers?

No. A mitigation system with documented installation by a licensed contractor and a post-test result below 4 pCi/L is widely viewed in Illinois real estate as a resolved issue. Most buyers and agents treat it as a positive sign of a responsible seller.