Contractor Certification in Missouri
Missouri has Zone 1 counties concentrated in the south-central and southwestern regions. MOHSS recommends testing all homes with basements in these areas.
Regardless of state licensing requirements, always verify that any radon contractor you hire holds current NRPP certification (nrpp.info) or NRSB certification (nrsb.org). These national certifications require passing a written exam and adhering to AARST ANSI installation standards.
Permit Requirements
Missouri does not require a statewide building permit for radon mitigation in existing single-family homes. An electrical permit is typically required at the local level when a new circuit or outlet is installed for the radon fan. Confirm with your local building department before work begins.
Radon Zones in Missouri
Missouri has counties in EPA Radon Zone 1 & 2. Zone 1 counties have the highest predicted average indoor radon levels. Even homes in lower-zone counties can test high — the only way to know your home's actual level is to test it with a certified test device.
What Missouri Homeowners Should Do
- Confirm your test result. At or above 4 pCi/L on a confirmed long-term test, proceed with mitigation. At 8+ pCi/L, act without further delay.
- Find 2–3 certified contractors. Search NRPP at nrpp.info or NRSB at nrsb.org for Missouri-based certified mitigators. Get written quotes.
- Confirm permit requirements. Ask your contractor: "Will you pull an electrical permit if new wiring is needed?" Confirm with your local building department.
- Schedule installation. Standard SSD installation takes 3–8 hours. Typical cost in Missouri: $800–$1,900.
- Post-mitigation test. Wait 24–48 hours after installation, then run a radon test. Target: below 4 pCi/L, ideally below 2 pCi/L.
Free Download: Missouri Radon Homeowner Checklist
Step-by-step checklist covering testing, permits, contractor selection, and post-mitigation testing. One printable page.
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