Radon Testing in O’Fallon, MO

Radon testing in O’Fallon, MO measures how much radon gas has built up inside a home, reported in picocuries per liter (pCi/L) against the EPA action level of 4.0 pCi/L. Air Sense Environmental places a calibrated continuous radon monitor in O’Fallon homes for a 48-hour closed-house test and delivers a documented report, so buyers, sellers and homeowners in St. Charles County know whether the house sits above the action level. O’Fallon radon testing starts with the number. A radon test is the only way to get that number for a specific O’Fallon address.

Is radon a problem in O’Fallon, MO?

Yes. St. Charles County is in EPA Radon Zone 2, where the predicted average indoor radon level is 2 to 4 pCi/L, and individual O’Fallon homes routinely test well above the 4.0 pCi/L action level. Missouri’s Department of Health and Senior Services reports that roughly one in three homes tested through its statewide program between 2003 and 2023 came back at or above 4.0 pCi/L. O’Fallon is the largest suburb of St. Louis, with more than 90,000 residents, and most of its housing went up between the 1990s and 2010s on poured basements set into St. Charles County’s silty clay soils.

Radon varies house by house rather than neighborhood by neighborhood. Two homes on the same O’Fallon street, built the same year by the same builder, can test at 1 pCi/L and 12 pCi/L because of what sits under each lot and how each foundation was sealed.

Which O’Fallon homes should be tested for radon?

Every O’Fallon home should have at least one radon test, and the EPA recommends retesting every two years for homes with a mitigation system and after any major renovation. The homes Air Sense Environmental tests most often in O’Fallon, MO:

• 1990s and 2000s subdivision homes on poured basements along Highway K and Highway N
• Homes in the older core near Main Street and the original town
• Walkout-basement homes on the sloped lots toward Dardenne Prairie
• Newer slab-on-grade villas and townhomes near Interstate 64
• Any home being bought or sold, where a radon test during the inspection period protects both sides of the deal

How does a radon test work in a O’Fallon home?

1. Monitor placement. A calibrated continuous radon monitor goes on the lowest level of the home that is or could be lived in, away from drafts, windows and exterior doors, following EPA and NRPP placement protocol. In O’Fallon, that usually means the basement, finished or not, because that is the level closest to the soil.
2. 48 hours of closed-house conditions. Windows stay closed and the HVAC runs normally while the monitor records hourly readings, with tamper detection so the result stands up in a real estate transaction.
3. A documented report. You receive the hourly data and the average reading against the 4.0 pCi/L action level, with a plain explanation of what the number means for your O’Fallon home.

How much does radon testing cost in O’Fallon, MO?

Radon testing prices in O’Fallon depend on the type of test and whether it is part of a real estate transaction. Air Sense Environmental publishes current pricing on its St. Louis radon testing cost guide and explains professional versus DIY testing on the main radon testing page, so the figures live in one place. Call 314-664-9807 for a quote for a O’Fallon address.

What happens if a O’Fallon radon test comes back at or above 4.0 pCi/L?

If the reading is at or above 4.0 pCi/L, the EPA recommends fixing the home, and the same Air Sense Environmental team designs and installs the system. See radon mitigation in O’Fallon, MO for how a sub-slab depressurization system is fitted to O’Fallon foundation types, and the St. Louis radon mitigation services page for the process, documented results and warranty. A post-mitigation test confirms the system brought the home below the action level.

Radon testing near O’Fallon: neighborhoods and nearby communities

Air Sense Environmental tests homes across O’Fallon, MO, including the Highway K corridor, the original town along Main Street and the neighborhoods toward Dardenne Prairie, in ZIP codes 63366 and 63368. Nearby communities with their own service pages:

• Radon testing and mitigation in St. Peters, MO
• Radon testing and mitigation in St. Charles, MO
• Radon testing and mitigation in Wentzville, MO
• All Air Sense Environmental service areas

Related from Air Sense Environmental: Indoor Air Quality Testing and Reviews & Projects.

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