Radon testing in the Helena area
With about half of tested Lewis and Clark County homes at or above 4 pCi/L in the state's data, a test is the first thing to do, and it's the only way to know your number.
A radon test answers two practical questions. Before a system goes in: does this house need one? After it goes in: is it working? Montana DEQ recommends testing in the lowest level of the home suitable for living in, and if that floor isn't used much, testing a higher-use room too.
What kinds of tests are there?
| Test type | How long | Best used for |
|---|---|---|
| Short-term kit | A few days | A first screening or a quick recheck |
| Long-term kit | 90 days or longer | A year-round average that covers a Helena winter |
| Continuous radon monitor | At least 48 hours, logged hourly | Home sales, post-mitigation tests, seeing daily swings |
How do I keep a test accurate?
- Set it in a lived-in room on the lowest level, such as a finished basement family room, not a storage crawl space.
- Keep windows and outside doors closed, apart from normal coming and going, for the length of a short-term test and for about 12 hours before it starts.
- Keep the device off the floor and away from exterior walls, drafts, the sump, the kitchen, bathrooms and heat registers.
- Don't move it once it's started, and write down the start and end times.
- Mail it to the lab promptly. Kits sitting in a hot car or on the counter for a week can give a bad read.
DIY kit or a radon professional?
A store-bought or DEQ kit is a fine first step for a house you live in. Montana DEQ has sold discounted mail-in kits through its Radon Control Program, with lab analysis included, while supplies last; call its hotline at 1-800-546-0483 to ask what's on offer. A measurement professional uses a calibrated continuous monitor, documents closed-house conditions and gives you a written report. That matters when a buyer, seller or lender needs a result they can rely on, and when you want to confirm a new system is doing its job.
My kit came back high. Now what?
DEQ's advice is to test twice before acting on an elevated reading. Run a second short-term test, or a long-term test if you have time, and if the average is still at or above 4 pCi/L, the EPA recommends mitigating. A radon company can then look at the foundation and quote a mitigation system.
When should I test again?
After a system goes in, DEQ says to test within the first month but no sooner than 24 hours after the fan is turned on, and to use an independent tester rather than the installer. With a system, retest at least every two years. Without one, DEQ encourages testing every two to five years, and again after major remodeling, such as finishing a basement.
We don't publish or quote prices. The radon company prices the job after it understands your foundation, and usually after someone has walked through the house, so treat any figure given over the phone as a starting point, not a quote.
Where we connect you with help
Common questions
Is winter a good time to test in Helena?
Yes. A house that's closed up with the furnace running tends to pull more soil gas, so a winter test shows something close to your highest levels. A long-term test averages the seasons.
Do newer houses in the valley need testing?
Yes. Age doesn't predict radon. Newer, tighter houses can test high, so test every home.
Related services
- Radon mitigation systems
- Crawl space and mixed foundations
- Radon for buyers and sellers
- Radon fan replacement and repair
More background: Montana radon guide.
Radon result came back over 4 pCi/L?
Call and get connected with a Helena-area radon company that can look at your foundation and design a system.