In an Illinois Emergency Management Agency study, 41% of Illinois homes tested for radon were above the 4 pCi/L action level ^[IL-4]. 56 of Illinois’ 102 counties are in EPA Radon Zone 1, the highest-potential zone ^[EPA-5].

RadonCosts lists 89 radon mitigation companies for Illinois. 83 of them have a mitigation professional on IEMA’s active licensee list ^[IL-3], and the rest hold NRPP or NRSB mitigation certification. Illinois requires an IEMA license, so check any installer without one before hiring (see below). 11 companies are based in neighboring states and hold an Illinois license.

Illinois at a glance

Illinois radon rules

• Licensing: IEMA licenses radon measurement and mitigation professionals. Look up any installer on IEMA’s active licensee search ^[IL-3]. Each RadonCosts listing shows the IEMA license number of the company’s mitigation professional.
• Real estate (Illinois Radon Awareness Act): before a buyer is obligated under a contract for residential property, the seller must give the buyer the IEMA pamphlet on radon and a disclosure covering any known radon test results and mitigation ^[IL-2]. IDPH notes the law doesn’t require testing or mitigation. It requires that buyers be informed and that existing test results be disclosed ^[IL-4].

Radon zones in Illinois’ largest counties

EPA zones show average predicted potential across a county, not your house. EPA says homes with high levels turn up in every zone ^[EPA-5]. Zone 2 Chicago suburbs still regularly test above 4 pCi/L, so test before you decide. County-level test results from IEMA weren’t available when we checked (the page returned an error). We’ll add them when it’s back.

Licensed installers in Illinois

Cities with the most listed companies: Plainfield (4), Elgin, Naperville, Schaumburg and Rockford (3 each). IEMA’s listing shows the counties each licensee serves, and so does each RadonCosts listing. Many cover the whole state.

What radon mitigation costs in Illinois

• IEMA and IDPH: typically $800–$1,200, depending on the house and the reduction method ^[IL-1][IL-4].
• National surveys: $805–$1,326, average $1,043. Angi’s Chicago figure is about $1,200 (estimate) ^[ANGI].
• What IL installers post online: 2 of 12 IL-listed websites we could read state a mitigation-system price or price range (crawl Nov 2, 2026). These are the companies’ own advertised figures, sometimes for a specific job type (for example new construction or activating a passive system). They aren’t quotes:
  • DuPage Radon Contractors: $1,100–$6,000 (source)
  • Inspect It Chicago, Inc.: $1,750–$3,000 (source)
• RadonCosts homeowner reports: not enough yet. Report what you paid.

FAQ

Does a radon mitigator need an Illinois license? Yes. Check the IEMA licensee list ^[IL-3]. Listings marked “national certification only” weren’t found on the IEMA list when we checked, so ask for their IEMA license number.

Do I have to test before selling in Illinois? No. You must give the buyer the radon pamphlet and disclose any known results ^[IL-2][IL-4].

I’m in Cook County (Zone 2). Should I bother? Yes. Zone is a county average. Only a test tells you about your home ^[EPA-2].

Data: IEMA Radon Tracking System active mitigation licensees (Nov 2, 2026), NRPP and NRSB searches (Nov 2, 2026), EPA radon zones, US Census 2024 estimates.