Ask most people what Colorado's radon disclosure law does, and they'll tell you it means every home sale comes with a radon test. That's not what the statute says.
Senate Bill 23-206, in effect since August 7, 2023, requires every residential sales contract in Colorado to carry a bold-type warning about radon risk and to disclose whatever the seller already knows: prior test results, any mitigation performed, whether a system is installed. What it does not require is that anyone actually test the property before selling it. A seller who has never run a radon test can comply fully by disclosing exactly that. No test, no violation. For a buyer relying on that disclosure to mean the air has been checked and cleared, that gap is the whole story.
In Grand Junction, where the geology puts the city in EPA Radon Zone 1 and local readings routinely run well above the national picture, that gap does more work than it does almost anywhere else in the state.
The Law Covers Paperwork, Not Air Quality
SB23-206 was written to close an information gap between sellers and buyers, and on paper it does that job well. It requires the sales contract to include the state health department's recommended language urging buyers to test before purchasing and to mitigate if levels come back elevated. It requires sellers to hand over any existing radon records, describe any concentrations detected, and disclose whether a mitigation system has already been installed. It requires a copy of the Colorado Department of Public Health and Environment's radon brochure to change hands alongside the contract.
None of that requires a fresh test. If the home has never been tested, the disclosure obligation is satisfied by saying so. The Colorado Real Estate Commission built forms around this exact structure, and the Division of Real Estate's broker guidance treats the paperwork requirement and the testing recommendation as two separate things: one is mandatory, the other is a strong suggestion.
That distinction matters more in Grand Junction than in most Colorado cities, because the odds that an untested home actually has a radon problem are higher here than almost anywhere else in the state.
Why Grand Junction Sits in the Alarm Zone
Radon forms from uranium decay in soil and rock, and the Western Slope's geology produces more of it than most of the country sees. Colorado's statewide indoor average runs around 6.4 picocuries per liter, already well above the EPA's action threshold of 4.0 pCi/L and nearly five times the national average of 1.3 pCi/L. Grand Junction itself frequently tests higher than the state average, with readings reported around 8.2 pCi/L in some local surveys. The city falls squarely into EPA Radon Zone 1, the agency's highest-risk classification.
None of that means every home has a problem. It means the baseline odds favor testing rather than skipping it, and it means a seller who discloses "never tested" isn't handing a buyer a clean bill of health. They're handing over an unknown in a market where the unknown skews elevated.
The Season Changes the Number
Here's the part that catches people off guard mid-transaction: radon readings in Grand Junction aren't stable across the year. Cold winters intensify what's called the stack effect. Heated indoor air rises and escapes through the upper part of a house, which pulls negative pressure at the bottom and draws soil gas up through foundation cracks and slab penetrations faster than it happens in warmer months. Local radon professionals report winter readings running 30 to 50 percent higher than summer readings in the same home. The EPA's own testing protocol calls for closed-house conditions, which happen naturally in winter and have to be manufactured artificially in summer testing.
That means a home tested in July and coming back at 3.0 pCi/L, comfortably under the action level, could plausibly read 4.0 to 4.5 pCi/L in January under the exact same roof. Nothing about the house changed. The season did.
| Testing Season | Typical Behavior | Transaction Implication |
|---|---|---|
| Summer (open-house conditions) | Readings often run lower; may understate true risk | A clean summer test can create false confidence for a winter closing |
| Winter (closed-house conditions) | Readings often run 30 to 50 percent higher | Closer to worst-case exposure; more reliable for action-level decisions |
For a buyer closing on a home this fall or winter, a summer test the seller discloses in good faith may not reflect what the house will actually read once the furnace kicks on and the windows stay shut for the season.
Where This Creates Friction at the Table
The disclosure requirement was built to reduce surprises. In practice, it can just move the surprise later in the transaction. A few ways this plays out locally:
- A seller discloses a summer test that passed, the buyer treats it as sufficient, and skips ordering their own. If they close in winter without retesting, they may be moving into a home with an actual reading above 4.0 pCi/L that nobody caught.
- A buyer orders their own test late in the process, during a cold snap, and it comes back elevated on a home that "passed" months earlier. Now mitigation has to happen inside whatever's left of the closing timeline, which forces a conversation about cost and who covers it.
- A rental conversion or investment purchase changes hands with an old test on file, and the new owner assumes it still applies without accounting for the seasonal swing.
None of these scenarios involve anyone acting in bad faith. They're a function of a law that mandates paperwork transparency without mandating that the underlying number be current.
The Practical Timeline, If a Test Comes Back High
A professionally installed radon mitigation system in Colorado typically runs between $1,500 and $3,500, depending on foundation type and house size. Regional contractor networks serving Grand Junction report handling closing-timeline mitigations within a 7 to 14 day window, including the post-installation verification test that lenders and inspectors want to see before they'll sign off. That's workable inside most Grand Junction escrow periods if it's flagged early. It's much tighter if a test result shows up in the final week before closing.
Locally, buyers and sellers navigating this generally work with InterNACHI-certified inspectors who handle radon testing as part of a full inspection, such as Fancy Fox Property Inspections, which serves Mesa County zip codes 81501 through 81507 including Orchard Mesa, Fruitvale, and Palisade. For standalone environmental testing, including radon alongside asbestos or mold sampling and phase-one assessments for real estate transactions, Grande River Environmental has served the Western Slope since 2011. NRPP-certified mitigation specialists round out the process once a test flags a level worth addressing.
What This Means Depending on Which Side of the Table You're On
If you're selling this fall or winter, ordering your own current-season test before listing gives you a real number instead of an old one, and it lets you address anything elevated on your own timeline rather than the buyer's. If you're buying, don't treat a summer disclosure as settled if you're closing in the cold months. A retest costs far less than discovering a mismatch after you've moved in.
Either way, this is exactly the kind of detail where having someone who understands both the transaction side and the construction side pays off. Radon mitigation systems are a straightforward add when they're planned into a renovation or a pre-listing improvement rather than bolted on as a last-minute fix under deadline pressure.
A Few Questions Worth Settling Before You List or Offer
Does Colorado require a radon test before a home can be sold? No. The law requires disclosure of any existing test results and mitigation history. It does not require that a test be performed.
What if the seller has never tested the property? They disclose that no test has been conducted, and that satisfies the legal requirement. The buyer is then free, and generally well advised, to order their own.
Who typically pays for mitigation if a test comes back elevated? There's no fixed rule. It's a point of negotiation between buyer and seller, and having the cost range and installation timeline in hand ahead of that conversation makes it far easier to reach a fair resolution quickly.
Radon disclosure in Grand Junction is one of those details that looks like simple paperwork until the timing works against you. If you're weighing a fall listing, a winter purchase, or a renovation that could use a mitigation system built in from the start, Kelly Maves and The Maves Group can walk through what that looks like for your specific property and timeline. Start Your Move with Maves.
