Do Illinois Home Sellers Have to Test for Radon?
No. Illinois law doesn’t require sellers to test for radon, but the Illinois Radon Awareness Act requires the seller to give the buyer a radon disclosure form and IEMA’s pamphlet, “Radon Testing Guidelines for Real Estate Transactions,” before the buyer is obligated under a purchase contract, along with any records the seller has that show elevated radon. Most buyers test anyway, because Kendall and Kane counties both sit in the EPA’s highest radon-potential zone.
By Kealan O’Neil | Updated October 18, 2026
Radon disclosure catches sellers off guard almost every time. They read “disclosure” and assume it means they have to test the house before they can sell it. That’s not what the law says, and the gap between what people assume and what’s required is where deals get complicated during attorney review.
This October 2026 update re-checks the radon disclosure rules against the Illinois statutes, IEMA, and the EPA, and adds the rules for new construction and rentals.
What Illinois Radon Disclosure Actually Requires
The Illinois Radon Awareness Act (420 ILCS 46) requires the seller of a home with one to four units to give the buyer two documents before the buyer is obligated under any contract to purchase:
- The pamphlet “Radon Testing Guidelines for Real Estate Transactions,” published by the Illinois Emergency Management Agency (IEMA), or an equivalent IEMA has approved
- The “Disclosure of Information on Radon Hazards,” whose wording is set out word for word in Section 10(b) of the Act
On the radon disclosure form, the seller initials whether high radon is known, whether records were provided, or whether the seller has no knowledge or no records. The buyer and agent initial their acknowledgments.
The law doesn’t require the seller to test or to install a mitigation system before closing. The duty is to share elevated-level records the seller already has, so if you tested two years ago and the number came back high, that report goes to the buyer whether or not you fixed it.
Timing matters too. If the disclosure happens after a buyer makes an offer, Section 10(c) says the seller must complete it before accepting and give the buyer a chance to review the information and possibly amend the offer.
Where to find the Illinois radon disclosure form PDF
IEMA’s real estate page hosts the required pamphlet in fact sheet and brochure formats. As of October 18, 2026, the disclosure PDF linked from that same page is titled for current and prospective tenants, not for sales, so don’t grab it for a listing.
For a sale, you need the version titled “For Residential Real Property Sales or Purchases,” which repeats the Section 10(b) wording. Your listing agent or attorney can supply it, and it’s worth checking that title line before anyone signs.
Which sales are excluded
Section 20 of the Act excludes court-ordered and foreclosure transfers, sales by an executor or trustee, transfers between co-owners or to a spouse or direct relative, inheritances, government transfers, and units on the third story or higher.
New construction isn’t on that list. The separate seller disclosure report exempts a new home that has never been occupied, but the radon act has no matching exclusion, so expect the radon form and pamphlet from a builder too, and ask your attorney to confirm they’re in the file.
How it fits with the seller disclosure report
The radon act runs alongside the Residential Real Property Disclosure Report. Statement 15 on that report asks whether the seller is aware of unsafe concentrations of radon on the premises, and “aware” means actual knowledge without any specific investigation.
So radon shows up in both places, but neither document replaces the other. The report doesn’t deliver the pamphlet or the radon warning statement, so both belong in the file before the buyer signs.
Why Radon Matters More in Kendall and Kane County Than You’d Think
Radon comes from uranium breaking down in soil and rock, and it seeps into a home through the foundation. Age doesn’t protect a house, so a new build in Grande Reserve can test as high as a hundred-year-old home near downtown Yorkville.
Here’s what the primary sources say about our area:
- The EPA’s Map of Radon Zones puts Kendall and Kane counties in Zone 1, the highest-potential category, where predicted average indoor levels may exceed 4 pCi/L. Will County, which covers part of Oswego, is in Zone 2. The EPA says the map isn’t a verdict on any one house and every home should be tested.
- The EPA’s action level is 4 pCi/L. At or above that number, the agency recommends fixing the home, and between 2 and 4 pCi/L it says to consider a fix. The average indoor level in American homes is about 1.3 pCi/L.
- IEMA estimates that more than 1,100 people in Illinois develop radon-related lung cancer each year.
- The Kendall County Health Department says test results show many Kendall County homes are at risk for high radon levels, and it offers test kits at its office at 811 W. John Street in Yorkville.
None of that means a home in Yorkville, Oswego, or Montgomery has a problem. It does mean that anywhere in Chicago’s Western Suburbs, sellers should expect a radon test and buyers should plan for one before signing.
New construction and the passive pipe rule
Since June 1, 2013, the Illinois Radon Resistant Construction Act has required all new residential construction, meaning single-family homes and buildings with two or fewer units, to include passive radon-resistant construction. That’s a vent pipe running from below the foundation to above the roof that relies on natural upward airflow.
A passive pipe isn’t a tested, working system. The law requires the pipe, not a test, and only a licensed radon contractor may add a fan to make it active, so test after move-in either way.
If you’re weighing a new build against resale, our guide to buying new construction in Yorkville, Oswego, and Montgomery covers the other line items to compare.
What Happens When a Buyer Asks for a Radon Test
A radon test isn’t part of the disclosure paperwork. Buyers add it during the home inspection period, and the result gets negotiated in the same window as any other finding under your inspection contingency.
IEMA’s real estate guidelines lay out how a transaction test should run:
- Use a licensed measurement professional. IEMA says it isn’t in the buyer’s or seller’s interest to rely on anyone else, so a seller’s own kit result carries less weight.
- Test each lowest livable area. A basement and a family room over a crawl space each get a test, and results aren’t averaged across areas.
- Run at least 48 hours, with two detectors side by side or one continuous monitor that records hourly.
- Keep closed-house conditions starting at least 12 hours before the test: windows closed, doors closed except for normal entry and exit, and no fans that pull in outside air.
- Leave the equipment alone. IEMA’s guidelines say interfering with a radon measurement is illegal in Illinois.
Sellers, those last two points are on you, so keep the windows shut and don’t move the device.
If the result is 4 pCi/L or higher
An elevated result usually settles one of three ways: the seller installs a mitigation system before closing, the seller gives a credit at closing so the buyer can handle it after, or the buyer accepts the home as-is.
The EPA says most homes can be fixed for about the same cost as other common home repairs, depending on the home’s size and design. Get written estimates from licensed mitigators instead of guessing at a number.
Put the details in writing: a licensed radon contractor installs the system, and a post-mitigation test runs within 30 days of installation, as the EPA recommends.
The mistake I see sellers make is treating a radon result like a deal-killer instead of a fixable line item. It’s a number, and numbers get negotiated.
Buying a Home to Rent Out? The Tenant Rules Changed in 2024
If you’re buying as an investment, radon records matter after closing too. For leases signed on or after January 1, 2024, Section 26 of the Act requires a landlord to give a prospective tenant IEMA’s “Radon Guide for Tenants,” copies of any records showing a radon hazard in the unit, and a tenant version of the disclosure form.
Tenants then get 90 days from the start of the lease to run their own test. If the result is above the action level and the landlord chooses not to mitigate, the tenant can end the lease.
That means a seller’s radon disclosure, old test reports, and mitigation paperwork all change the math on a rental. Our guide to buying investment property in Oswego covers the other numbers to run before you write an offer.
What the Right Real Estate Agent in Yorkville, IL Does About Radon Before You Sign
Choosing a real estate agent in Yorkville, IL often comes down to who catches small items before they become fights. Here’s the radon checklist I’d hold any agent to, including ours:
- Confirm the sales version of the radon disclosure and the IEMA pamphlet reach the buyer before the buyer signs.
- Ask for every elevated test report and any mitigation paperwork, and look for a labeled pipe, fan, and gauge or alarm.
- Book the radon test on day one of the inspection period so the 48-hour run and the report fit the deadline.
- Write the remedy into the attorney review terms, including who hires the licensed mitigator and when the post-mitigation test happens.
Radon Disclosure Questions From Yorkville, Oswego, and Montgomery Buyers and Sellers
Buyers and sellers going through this for the first time usually ask some version of these questions.
Do I have to test my house for radon before I sell it in Illinois?
Where do I get the Illinois radon disclosure form PDF for a home sale?
What radon level is considered unsafe in Illinois?
Does a new construction home in Yorkville need a radon test?
Who pays for radon mitigation in Illinois, the buyer or the seller?
Radon disclosure is a small piece of paperwork with real negotiating weight behind it, especially in a county the EPA flags for higher radon potential. Whether you’re selling in Yorkville or deciding what to do with an elevated result in Oswego or Montgomery, talk through your situation rather than guessing at what’s standard.
If you’re working through this for your own home anywhere in Chicago’s Western Suburbs, I’m happy to walk you through the paperwork, the test, and the negotiation. Call or text Kealan at 630-425-8815.
This post is part of our Illinois purchase contract guide. The other two required disclosures are covered in our posts on the Illinois seller disclosure report and lead paint disclosure.
About Kealan O’Neil
Kealan O’Neil is the Designated Managing Broker and founder of O’Neil Property Group, an independent real estate brokerage based in Yorkville, Illinois. He and his team help buyers and sellers in Yorkville, Oswego, Montgomery, and the surrounding Kendall and Kane County communities, and he owns and manages a local rental portfolio, so he approaches every decision as both a broker and an investor. Call or text Kealan at 630-425-8815.
This post is general information about real estate in the Fox Valley, not legal, tax, or financial advice. Real estate laws, tax rules, and municipal ordinances change, and how they apply depends on your specific situation. Talk with a licensed attorney, CPA, or lender before making decisions about a purchase, sale, or tax matter. O’Neil Property Group is a licensed Illinois real estate brokerage.