What this covers
Radon is a colorless, odorless gas that comes from soil and rock and can collect in a home, so the only way to know the level is to measure it. A qualified tester places a passive test device or a continuous electronic monitor in the lowest level that is lived in or could be, away from drafts, sumps and exterior walls, and keeps closed-house conditions for the test period. Passive devices go to a lab; continuous monitors log readings hour by hour. The report gives the average concentration over the test and, for monitors, how it varied, which tells you whether mitigation is worth discussing.
When to call
- A home that has never been tested.
- A home you are buying or selling.
- A finished basement or new living space on the lowest level.
- A mitigation system that was installed and needs a follow-up test.
What to expect
- Set conditionsWindows and exterior doors are kept closed for the test period, apart from normal coming and going.
- Place the deviceThe tester sets the device at the right height and location in the lowest lived-in level.
- MeasureThe device runs for the test period, usually a few days for a short-term test.
- ReportThe lab or the monitor's log gives the average level and the tester explains the result.
Get a certified company
Look up a certified company by ZIP code. Every company's license, insurance and trades are verified before it is listed, and placement is never paid.
Questions people ask
Short-term or long-term test?
A short-term test gives a result in days and is common in a sale. A long-term test runs for months and reflects seasonal change more closely.
Why does the house need to stay closed?
Open windows dilute the air and give a reading that does not reflect normal conditions. Closed-house conditions keep the result comparable.
Do neighbors' results tell me mine?
No. Radon levels can differ widely between houses on the same street, so each home is tested on its own.
Related: Radon mitigation · Home inspection · All inspections and testing
This page describes what the service involves. The company you hire sets the scope, the schedule and the price, and your contract is with that company. We verify credentials and collect reviews from real jobs. We do not guarantee any company's workmanship. Safety steps are general guidance. When in doubt, leave the home and call 911.