Radon in Illinois: What Homeowners Need to Know

Illinois has a radon problem that most homeowners don't know about. The state's average indoor radon level of approximately 4.6 pCi/L exceeds the EPA action level of 4 pCi/L — meaning the average Illinois home, if untested, should be presumed to need mitigation. Over 40% of Illinois homes tested by the Illinois Emergency Management Agency (IEMA) have come back above 4 pCi/L.

Illinois Radon Risk by Region

Not all of Illinois carries equal risk. EPA radon zones divide the state roughly as follows:

Zone 1 (highest risk): Northern and central Illinois — Chicago metro, Rockford, Peoria, Springfield, the Quad Cities. These areas consistently produce the state's highest residential readings.

Zone 2 (moderate risk): Parts of east-central Illinois and some southern counties. Still warrant testing.

Zone 3 (lower risk): Far southern Illinois near the Shawnee Hills. Still recommended to test.

The Chicago metropolitan area — Cook, DuPage, Lake, Will, Kane, and McHenry counties — sits predominantly in Zone 1. Chicago's dense older housing stock, with millions of homes built before 1960 featuring full basements, creates significant cumulative radon exposure across the region.

Illinois Radon Geology

Illinois's radon originates from two primary sources:

Glacial till: Most of northern and central Illinois is covered in uranium-bearing glacial deposits left by Pleistocene ice sheets. This till covers the bedrock and produces radon that migrates through permeable soils toward building foundations.

Sedimentary bedrock: Limestone, shale, and coal-bearing formations underlie much of central and southern Illinois. Some of these formations produce significant radon in areas with shallow overburden.

What Radon Mitigation Costs in Illinois

Illinois mitigation costs vary by region and foundation type:

| Region | Typical cost range |

|---|---|

| Chicago metro | $900–$2,200 |

| Rockford, Peoria, Springfield | $800–$1,700 |

| Central Illinois (smaller cities) | $750–$1,500 |

Foundation-type variations:

• Poured concrete basement: $800–$1,300
• Block basement: $1,000–$1,700
• Crawl space: $900–$1,600
• Slab-on-grade: $850–$1,400

Illinois IEMA Licensing — What Makes Illinois Different

Illinois has its own state licensing requirement on top of national certification. Radon mitigation contractors must hold a license from the Illinois Emergency Management Agency (IEMA) — not just NRPP or NRSB national certification.

This matters when hiring. Always verify:

1. IEMA license: Check at iema.illinois.gov or ask the contractor for their license number
2. NRPP or NRSB national certification: Verify at nrpp.info or nrsb.org

Contractors who hold only national certification and not an IEMA license are operating outside the law in Illinois. Unlicensed contractors have no accountability mechanism if the system fails.

The Chicago-Area Radon Challenge

Chicago's housing stock presents specific challenges:

Older brick homes: Chicago's bungalow belt and two-flats, built between 1900 and 1960, often have stone or brick foundations that require more suction points and complex pipe routing.

Finished basements: Popular in Chicago suburbs, finished basements complicate access for sub-slab suction installation.

Urban lot constraints: Chicago's dense urban layout means exterior pipe runs often aren't feasible, requiring interior routing through closets, walls, or utility chases.

The result is that Chicago-area mitigation costs often run at the high end of Illinois ranges — $1,200–$2,200 for complex urban homes.

Testing Your Illinois Home

Before hiring a mitigator, test:

• Short-term test (48–96 hours): Charcoal canister, available at hardware stores. Mail-in results in 3–5 days. Good for quick answers or real estate transactions.
• Long-term test (90+ days): Alpha track detector. More accurate representation of annual average exposure. Better for understanding real-world risk.

The EPA recommends testing during heating season (October through March) for the most conservative results. Illinois homes tested in winter often return higher readings than summer tests due to tighter building envelopes.

FAQ

Does Illinois require radon disclosure when selling a home?

Illinois does not have a mandatory radon disclosure law, but the Illinois Residential Real Property Disclosure Act requires sellers to disclose known material defects. If a seller knows their home has elevated radon, disclosure is expected. Buyers routinely request radon inspections as a contingency.

Is radon a problem in newer Illinois homes?

Newer homes (post-2000) built with radon-resistant new construction (RRNC) features — passive sub-slab systems, vapor barriers, sealed penetrations — have a built-in foundation for mitigation. However, RRNC features alone don't guarantee safe levels. These homes may still need an active fan added to the passive system.

What's the fastest way to get a certified mitigator in Illinois?

Use RadonBase to search NRPP-certified mitigators in your area. Filter by IEMA license and verify credentials before scheduling.

Find an IEMA-licensed radon mitigator in Illinois →