Radon testing
You can't guess your radon level from the neighbors or the zone map. A test is the only way to know.
Testing answers two questions: does this house need a mitigation system, and, once a system is in, is it doing its job? Montana DEQ recommends testing the lowest occupied floor, and testing again after structural changes or when you start using a lower floor that sat empty before.
Which kind of test should I use?
| Test | Length | Good for |
|---|---|---|
| Short-term kit (charcoal) | 2 to 7 days, typically | A first look, or a quick recheck |
| Long-term kit (alpha track) | 90 days to a year | Your year-round average, through a Billings winter and summer |
| Continuous monitor | 2 days or more, hour by hour | Real estate deals, post-mitigation tests, seeing swings |
How do I get an accurate result?
- Set the test on the lowest level you live on, such as a finished basement, not an unused crawl space.
- Keep windows and outside doors shut, apart from normal coming and going, starting 12 hours before a short-term test and for its whole length.
- Keep it away from drafts, exterior walls, the sump, the kitchen and bathrooms, about breathing height off the floor.
- Skip short-term tests during big wind events if you can; strong wind and pressure swings can push results around.
- Mail the kit within the time the instructions give. Montana DEQ's mail-in kits ask for return within a week of finishing.
Kit or professional?
A kit is a fine first step for a house you live in. Montana DEQ has offered discounted mail-in kits through its Radon Control Program, with lab analysis and return postage included, while supplies last; call its hotline at 1-800-546-0483 to ask what's available. A measurement professional brings a calibrated continuous monitor, sets it up under closed-house conditions and gives you a written report, which matters for home sales and for checking a new system.
My result is high. What next?
At or above 4 pCi/L, the EPA recommends fixing the home. If you used one short-term kit, run a second test or a long-term test to confirm, then talk to a certified mitigation company. Montana DEQ recommends using an independent tester for the post-mitigation test so the installer isn't grading its own work.
How often should I retest?
Montana DEQ encourages retesting every two to five years even if your house tested low, because ground disturbance, weather and changes to the house can all shift levels. With a mitigation system in place, retest at least every two years.
The radon company sets the price after it learns about your house, and usually after someone has looked at the foundation. We don't quote prices, and a number given over the phone is only a rough starting point.
Where we connect you with help
Common questions
Is winter a good time to test in Billings?
Yes. A closed-up house with the furnace running tends to pull in more soil gas, so a winter test shows something close to your worst case. A long-term test smooths out the seasons.
Do newer homes in the West End need testing?
Yes. Newer, tighter houses can still have high radon. Test every home, whatever its age.
Related services
- Radon mitigation systems
- Crawl space and slab radon
- Radon for home buyers and sellers
- Radon fan replacement and repair
More background: Montana radon guide.
Got a radon number you don't like?
Call now and a local radon mitigation company will look at your house and quote a system.