Radon Mitigation in St. Louis, MO

Radon Mitigation in St. Louis, Missouri

St. Louis and the surrounding bi-state metro area sit on limestone and shale bedrock typical of the Ozark Plateau transition zone, where uranium-bearing formations produce consistent radon across the region. Missouri averages 3.5 pCi/L statewide, but the St. Louis metro — particularly St. Louis County, St. Charles County, and the Metro East counties in Illinois (Madison, St. Clair) — frequently tests between 4 and 14 pCi/L, with many homes exceeding the EPA action level.

Why St. Louis Has Radon Concerns

Northern Missouri and the St. Louis metro sit in the transition between EPA Zone 1 and Zone 2. St. Louis County and St. Charles County are classified Zone 1. The region's geology includes Ordovician-era limestone and dolomite overlain by thin glacial deposits. The Ozark Uplift to the south influences bedrock mineralogy across the St. Louis area. St. Charles County, with its hilly terrain along the Missouri River corridor, tests consistently higher than St. Louis City proper.

St. Louis's Illinois suburbs — Belleville, O'Fallon, and Edwardsville — sit in Madison County, which is Zone 1 in Illinois and tests among the state's highest radon areas. Homeowners on both sides of the Mississippi River should treat the St. Louis region as an elevated-risk area.

Radon Mitigation Costs in St. Louis

A standard radon mitigation system in St. Louis costs $1,000 to $2,100 for most homes. This includes:

• Sub-slab depressurization system installation
• One primary suction point
• PVC piping routed through home and vented above roofline
• Radon fan installation
• System testing and certification

Cost factors in St. Louis:

• Foundation type: Poured concrete slabs ($1,000-$1,500) vs. older block or stone foundations ($1,400-$2,100)
• Bi-state work: Contractors must hold Missouri AND Illinois credentials for cross-river work; verify accordingly
• Finished basements: Popular in St. Charles County; adds $300-$600
• Crawl spaces: Some South County and Webster Groves homes have crawl spaces; add $400-$700

Radon Contractor Standards

Missouri requires NRPP or NRSB certification. Illinois requires state certification through IEMA. For Illinois-side suburbs, verify the contractor holds Illinois IEMA credentials.

A certified St. Louis mitigator will:

• Perform sub-slab diagnostics before system design
• Install to EPA standards
• Post-test to confirm radon below 2 pCi/L
• Provide warranty

Getting Started in St. Louis

Test Your Home — Order a radon test kit or hire a professional. Results in 2-7 days. St. Charles County and Zone 1 areas on the Illinois side test highest.

Get Certified Quotes — Ensure contractors are licensed in your state. Contact 2-3 certified mitigators.

Install and Verify — One-day installation. Post-test confirms system effectiveness.

Finding a Certified Mitigator in St. Louis

Find a Certified Mitigator in St. Louis →

St. Louis is Missouri's largest radon mitigation market with 90+ certified contractors across the bi-state region. Average cost is $1,100-$1,800. St. Charles County and the Illinois Metro East test highest in the metro.

St. Charles County and Metro East are Zone 1. Test your St. Louis home today.