St. Louis Metro · Missouri & Illinois
Radon Testing for Home Inspections
Radon testing for home inspections gives buyers and sellers a documented reading inside the inspection window.
We arrange the test, and an IEMA-licensed radon measurement professional places continuous radon monitors under EPA closed-house conditions and returns a report you can put straight into the transaction file.
Results come back in two to three business days.
What Your Number Means
At or above 4.0 pCi/L the EPA recommends mitigation. Below it, no action is required.
Built to performThe Transaction
Radon Testing During a Real Estate Transaction
Radon usually comes up during the inspection period, when there is a fixed window to get answers.
A reading at or above 4.0 pCi/L is the EPA action level and commonly triggers a repair request or a credit. Having the number early gives both sides room to negotiate.
Protocol
Closed-House Conditions Explained
A valid short-term test requires closed-house conditions, starting twelve hours before the test and continuing throughout.
- Keep windows and exterior doors closed
- Run heating and cooling systems normally
- Do not run whole-house fans or window units that draw outside air
- Leave the monitor undisturbed where it is placed
Placement
Where the Monitor Goes
The device goes in the lowest livable level of the home, away from drafts, exterior walls, and direct sun.
Placement affects the result, which is one reason a professional test carries more weight in a transaction than a hardware-store canister.
Deliverable
What the Report Includes
- The average radon level in pCi/L
- Hourly readings across the full test period
- Placement location and test conditions
- Certification details for your file
Existing Systems
When the House Already Has a Mitigation System
A system on the house does not by itself prove the radon level is low.
Systems age and fans fail, and a seller may not know when anyone last tested. Check the manometer on the vent pipe, then test.
Scheduling
Timing Around Your Inspection Window
Tell us your deadline when you call.
If the result requires mitigation and the closing date is fixed, that sequence gets tight quickly, so it is worth starting the test in the first days of the window.
In the Field
Where Monitors Go
Common Questions
Frequently Asked Questions About Radon Testing for Home Inspections
Is a home radon test accurate?
A professional radon test is reliable enough for a real estate decision when it follows standard protocol: closed-house conditions, at least 48 hours of testing, correct placement in the lowest livable level and safeguards against tampering. Ask for a report with hourly readings across the full test period, so an unusual spike or interference shows up in the data instead of hiding inside a single average.
What time of year is best to test for radon?
For a home sale, the right time is during the inspection window, because the contract sets the deadline, not the season. Winter tests tend to show higher, worst-case levels, while summer results can read lower. If a summer result lands just under the EPA action level of 4.0 pCi/L, a follow-up test in the heating season gives a fuller picture of year-round exposure.
Is a radon test required when buying a home in Illinois?
No. Illinois does not require a radon test to buy or sell a home, but the Illinois Radon Awareness Act requires sellers of most residential property to give buyers the state’s radon disclosure and IEMA’s radon pamphlet before the buyer is bound by a contract. Missouri does not require a radon test to sell a house either. In both states, most buyers order a test during the inspection period.
Should you get radon testing on a home inspection?
Yes, adding a radon test to a home inspection makes sense for most buyers. The EPA recommends testing every home, and it identifies radon as the leading cause of lung cancer among non-smokers. You can’t see or smell radon, so testing is the only way to know the level in a particular house. A short-term test during the inspection period gives you a result while you can still talk about next steps. Air Sense can arrange testing through a separately licensed radon measurement professional.
Get Your Number
Inspection deadline coming up?
Give us the address and the deadline and we will confirm timing.