Montana law doesn't require a home seller to test for radon, but it does require disclosing any test the home has already had, plus proof of any mitigation (Montana Radon Control Act, MCA 75-3-606). The catch shows up after that: real Montana mitigation contractors report being booked six to eight weeks out, while a typical inspection contingency runs seven to ten days (Murphy Radon, 2026). A missed call during that window doesn't just cost a job — it can cost the closing.
What Montana's radon law actually requires
The Montana Radon Control Act (MCA 75-3-606) requires every seller of residential property to include a standard radon warning statement on a document signed at or before an offer — the boilerplate language about radon being a naturally occurring gas that can pose health risks at high concentrations. It does not require testing. But if the seller already knows the results of a prior test, the law requires handing the buyer a copy of those results and any evidence of mitigation before or at the time the buyer signs. A seller who complies is shielded from liability over radon; simply handing over test results doesn't itself create a contingency or a right to back out unless the purchase contract spells that out separately.
In practice, that pushes most of the actual decision-making onto the inspection period rather than the disclosure form. A buyer's inspector orders a short-term radon test, the result comes back during a contract contingency window that's commonly negotiated at seven to ten days, and if the number comes back high, the buyer and seller are suddenly negotiating a fix on a clock neither of them set.
The real bottleneck isn't the test. It's getting on the schedule.
A radon mitigation system itself is not a slow job. Bozeman Radon and Mold puts a typical residential install at three to six hours in a single visit, and Pure Air Solutions, in Missoula, says most systems go in within a day (Bozeman Radon and Mold, 2026; Pure Air Solutions, 2026). The delay isn't the work — it's getting a licensed crew to show up at all. Murphy Radon, which serves Missoula, Ravalli, and Mineral counties, says on its own site that it's "consistently booked 6-8 weeks in advance" (Murphy Radon, 2026). Bozeman Radon and Mold is direct about why that matters for a home sale: "elevated radon levels discovered during inspection are one of the most common reasons deals stall," which is exactly why the company says it prioritizes real estate jobs to fit inside a buyer's contingency window (Bozeman Radon and Mold, 2026).
| Step | How long it actually takes | How long the deal gives you |
|---|---|---|
| Short-term radon test | 2-5 days of monitoring | Part of a 7-10 day contingency |
| Lab result turnaround | A few days by mail-in kit | Same 7-10 day window |
| Mitigation system install | 3-6 hours, one visit | Not the bottleneck |
| Getting a crew scheduled | Commonly 6-8 weeks out | Routinely blows the contingency |
Line those up and the mismatch is obvious: everything about the actual fix takes hours. Everything about getting a contractor to show up takes weeks. A seller who calls three radon companies and reaches voicemail at two of them isn't losing a little time — they're losing the only window the buyer's contract gives them.
Why fall raises the stakes
Montana's own regulator doesn't sugarcoat how common a high reading is here. The state's Department of Environmental Quality says roughly half of the homes tested for radon in Montana come back at or above the EPA's 4.0 pCi/L action level, and DEQ Air Quality Bureau Chief Bo Wilkins has noted that "weather, ground disturbances and changes to your home have the potential to impact radon levels" (DEQ Radon Action Month, 2026). DEQ's own testing guidance tells homeowners running a short-term test for a real estate deal to close up the house and run it "as if it were the winter heating season," regardless of the actual season outside (Montana DEQ, 2026) — because that's when radon tends to concentrate indoors. Fall testing in Montana is, by the state's own instructions, already being run under simulated winter conditions.
Layer that onto a housing market where plenty of buyers are trying to close and move before snow settles in, and a fall listing has less slack than a spring one, not more. A seller who assumed radon was a box to check on a disclosure form finds out otherwise the moment the inspection report lands.
What this looks like for a Flathead Valley company
Big Mountain Insulators, based in Whitefish, has been serving Flathead County on radon work since 1986 — Whitefish, Columbia Falls, and the surrounding valley (Big Mountain Insulators, 2026). A company with that kind of tenure has already outlasted plenty of Montana winters and plenty of closings that came down to the wire. What it can't outrun is a phone that only gets answered during business hours in an industry where the calls that matter most — "my inspection just came back high, my contingency closes in nine days" — don't wait for 8 a.m.
- A caller with a live contingency deadline needs to be captured and prioritized the moment they call — not queued behind routine testing inquiries.
- An after-hours or lunch-hour missed call from a title company or realtor coordinating a closing is a different kind of urgent than a routine testing request.
- A radon company operating near its 6-8 week capacity has the least room in the industry to let a call go to voicemail and hope for a callback.