Montana has some of the highest radon levels in the western United States. The state’s diverse geology — including granitic intrusions, uranium-bearing phosphate deposits, and deep glacial valleys — produces radon concentrations that routinely exceed the EPA action level in homes across the state. Western Montana’s mountain corridors and valley floors are particularly affected.
Radon Risk in Montana: What the Data Shows
The Montana Department of Environmental Quality estimates that approximately 45 percent of Montana homes have radon at or above 4 pCi/L — nearly double the national average. The EPA classifies nearly the entire state as Zone 1 or Zone 2. Missoula, Bozeman, Helena, Kalispell, and Butte all fall in high-risk zones.
Montana’s western counties sit on fractured granite and metamorphic rock with naturally high uranium content. The mountain valleys trap cold, dense air — and with it, radon — creating a chimney effect that draws soil gas upward into homes. Eastern Montana adds uranium-bearing shale and lignite from the Williston Basin sedimentary formations. No part of Montana can be considered low-risk without testing.
How Radon Mitigation Works
The standard solution for most Montana homes is sub-slab depressurization (SSD). A licensed contractor cores through the foundation slab, installs a PVC pipe, and connects it to a continuously running exhaust fan. The fan draws radon-laden soil gas from beneath the slab and exhausts it safely above the roofline — before it can enter your living space.
For homes with crawl spaces, a sealed ground cover membrane with a dedicated exhaust fan accomplishes the same result. Both methods are proven: properly installed systems reduce indoor radon by up to 99%. Systems operate 24 hours a day, every day, and require minimal maintenance.
High-Risk Counties in Montana
Radon can be elevated anywhere in Montana, but the following counties report the highest concentrations based on state testing data:
- Yellowstone County (Billings)
- Cascade County (Great Falls)
- Missoula County
- Gallatin County (Bozeman)
- Flathead County (Kalispell)
- Lewis and Clark County (Helena)
- Ravalli County (Hamilton)
- Silver Bow County (Butte)
- Lake County (Polson)
- Park County (Livingston)
If you live in or near Billings, Great Falls, Missoula, Bozeman, and Helena, testing your home is a straightforward, low-cost step. For a full breakdown of what a professional installation involves, see our radon mitigation service guide.
Radon Levels: How to Read Your Results
| Level (pCi/L) | Risk | Recommended Action |
|---|---|---|
| Below 2 | Low | No action needed. Retest every 2–5 years. |
| 2 to 3.9 | Moderate | Consider mitigation. Confirm with a long-term test. |
| 4 and above | EPA action level | Mitigate promptly. |
| 8 and above | High | Mitigate as soon as possible. |
Radon Mitigation Cost in Montana
- Standard sub-slab depressurization: $900 – $1,600
- Complex systems (multiple suction points): $1,600 – $2,800
- Crawl space systems: $1,200 – $2,200
- Post-mitigation follow-up test: $25 – $50
Montana homeowners typically pay $1,000 to $1,600 for a standard system. Costs can run higher in remote areas due to travel time and materials logistics. Montana DEQ provides free radon test kits to residents. Some tribal nations may offer additional radon programs — contact your local tribal health department.
Montana Radon Contractor Certification
Montana does not require state licensing for radon professionals. The Montana DEQ recommends using contractors certified through the NRPP or NRSB. Given Montana’s high radon prevalence, hiring a nationally certified contractor is strongly advisable. Verify certification before hiring. Always verify contractor credentials before hiring. The state radon program is managed by the Montana Department of Environmental Quality — Radon Program.
Additional resources: EPA Radon | WHO Radon and Health
Frequently Asked Questions
Is radon a real problem in Montana?
Absolutely. Montana is one of the highest-radon states in the entire country, not just the West. The DEQ estimates approximately 45% of Montana homes exceed the EPA action level. The EPA classifies nearly the entire state as Zone 1 or Zone 2. Every Montana home should be tested.
How much does radon mitigation cost in Montana?
Radon mitigation in Montana typically costs $900 to $2,800 depending on foundation type, home size, and location. Most homeowners pay $1,000 to $1,600. Rural and remote areas may be higher due to contractor travel costs. Get a free quote below.
Are radon contractors licensed in Montana?
Montana does not require state licensing. The DEQ recommends NRPP- or NRSB-certified contractors. Always verify national certification credentials before hiring any radon contractor in Montana.
How long does radon mitigation take?
Most residential installations are completed in 3 to 5 hours. The system begins working immediately. Schedule a follow-up test 24 to 48 hours after installation to confirm radon levels have dropped below 4 pCi/L.
When should I test for radon in Montana?
Test immediately if you have not done so — Montana’s radon risk is among the highest in the country. Also test before buying or selling any property, after foundation work, and every two years if a mitigation system is installed. Montana’s cold climate and long heating season concentrate radon indoors significantly.
Get a Free Radon Mitigation Quote in Montana
If your Montana home has tested above 4 pCi/L — or if you have never tested — the right move is to act now. Fill out the form below and we will connect you with a licensed Montana radon contractor for a free quote.
