Skip to content 
Professional Radon Testing in St. Louis, MO
The only way to know if your St. Louis home has dangerous radon levels is to test for it.
ORF Home Inspections provides professional radon testing across St. Louis and the surrounding areas so you can protect your family from long-term exposure.
The Environmental Protection Agency identifies radon as the second leading cause of lung cancer in the United States, right behind smoking. Missouri sits in a moderate to high radon zone, and many St. Louis homes test above the EPA action level of 4.0 pCi/L. Testing takes the guesswork out of the equation and gives you a clear number to act on.
How Our St. Louis Radon Testing Works
We use continuous radon monitors that record radon levels every hour over a minimum 48-hour testing period. This method gives us accurate data that reflects real conditions inside the home. Unlike charcoal test kits you find at hardware stores, our monitors track fluctuations throughout the testing window and deliver precise hourly readings.
What to Expect During Radon Testing
- We place the continuous radon monitor on the lowest livable level of the home
- The monitor records radon concentrations every hour for at least 48 hours
- We maintain closed-house conditions during the test for accurate results
- We retrieve the monitor and calculate the average radon level
- You receive a detailed report with hourly readings and the final average
Closed-House Conditions
Accurate radon testing requires closed-house conditions. This means keeping all windows and exterior doors shut during the test period. Normal entry and exit through doors is fine, but you should not leave doors or windows open for extended periods. We walk you through these requirements before we start the test so you know exactly what to do.
Understanding Your Radon Test Results
The EPA sets 4.0 pCi/L (picocuries per liter) as the action level for radon in homes. If your St. Louis home tests at or above this number, the EPA recommends installing a radon mitigation system to reduce the levels.
- Below 2.0 pCi/L: Low risk. No action required at this time.
- 2.0 to 3.9 pCi/L: Moderate levels. Consider mitigation, especially in homes with children or long-term occupants.
- 4.0 pCi/L and above: EPA action level. Install a radon mitigation system to bring levels down.
No level of radon exposure is completely safe. The World Health Organization sets its recommended action level at 2.7 pCi/L, lower than the EPA standard. We present the numbers clearly and let you make an informed decision about next steps.
When Should You Test for Radon in St. Louis?
Buying a Home
Every homebuyer in St. Louis should include radon testing as part of their inspection process. We run the radon test alongside your home inspection so results come back before your inspection contingency deadline. If levels come back high, you can negotiate with the seller to install a mitigation system before closing.
Selling a Home
Sellers who test for radon before listing remove a potential obstacle from negotiations. A clean radon test gives buyers confidence. If levels come back elevated, you can install mitigation proactively and present the results as part of your pre-listing inspection package.
Living in Your Current Home
The EPA recommends testing every home for radon, regardless of age or construction type. If you have never tested your St. Louis home, now is the right time. Radon levels can change over the years as foundations settle, cracks develop, and soil conditions shift. Even homes that tested low five or ten years ago should get retested.
After Renovation or Foundation Work
Any work that alters your foundation or basement can change how radon enters the home. New cracks, sealed openings, added ventilation, and changes to HVAC systems all affect radon levels. Test again after major renovations to confirm your home still falls within safe limits.
Why St. Louis Homeowners Choose ORF Home Inspections for Radon Testing
We test homes for radon across St. Louis every week. We use professional-grade continuous monitors that deliver accurate, defensible results. Our reports include hourly data, average concentrations, and clear explanations of what the numbers mean for your home.
We also offer radon testing as an add-on to any of our inspection services. Bundle it with your home inspection, mold inspection, or VA/FHA inspection and get everything done in one visit. We serve St. Louis City, St. Louis County, St. Charles County, Jefferson County, and surrounding communities.
