Do You Need a Radon Test When Buying a Home in Gunnison, CO?

Yes, I recommend it. Gunnison County is listed in EPA Radon Zone 1, the highest-risk tier, and Colorado sellers must disclose radon if it is known to exist or has ever existed in the home. A short-term test during your inspection period takes about two to five days, and a fix, if one is needed, is usually a standard system rather than a deal-breaker.

This is general information, not medical or legal advice. Radon levels vary house to house, even next door to each other, so only a test of the specific home tells you anything.

What is radon, and why does it matter?

Radon is a naturally occurring radioactive gas that forms when uranium in soil and rock breaks down. It can seep into a home from the ground beneath it. The Colorado Department of Public Health and Environment (CDPHE) says radon causes about 500 lung cancer deaths a year in Colorado and calls it the leading cause of lung cancer among non-smokers in the United States. You cannot see or smell it, which is why testing is the only way to know.

Is radon a concern in Gunnison County?

The radon-testing directory radonresources.com places Gunnison County in EPA Radon Zone 1 and says predicted average indoor screening levels there are above 4 pCi/L. (A pCi/L, or picocurie per liter, is the unit used to measure radon in air.) The same page lists an average of 8.00 pCi/L from 17 user-submitted tests in two county cities. That is a very small, self-selected sample, so I would not treat it as a county average. Statewide, a Walking Mountains real estate guide says about half of Colorado homes test above the EPA action level of 4 pCi/L and that the whole state, not just the mountains, is considered high risk.

What is the radon action level?

The EPA action level is 4 pCi/L. Results under 4 still carry some risk, and the EPA suggests considering a long-term test in that case. If a test comes back at 4 or above, the usual next step is to get bids from a certified mitigation contractor.

How does a radon test work during a home purchase?

Per the Boulder County guide to radon in Colorado real estate transactions and the Walking Mountains guide:

• Short-term test: About two to five days, typically used at resale. The home is kept closed (windows and exterior doors shut except normal entry and exit) for 12 hours before the test starts and throughout it.
• Where it goes: The lowest level of the home that could be lived in, even if it is unfinished.
• Who does it: A tester certified by NRPP or NRSB (the national radon proficiency programs).
• Long-term test: 91 days to a year under normal living conditions, usually done after move-in if the short-term result was under 4.

In Gunnison, where winter inspections are common, build the radon test into the same inspection window as the rest of your due diligence so it does not hold up closing.

What does the seller have to disclose?

On Colorado's Seller's Property Disclosure form, radon is a listed hazard. The seller must disclose it if it is known to exist or has ever existed, even if past results were below 4 pCi/L, and should provide copies of all prior test results and disclose any existing mitigation system.

Who pays if the test is high?

There is no legal requirement that the seller pay. Per the Boulder County guide, the cost is negotiated like any other repair, often using bids from certified contractors. Some buyers ask the seller to pay, some split the cost, and some buy the home and mitigate after moving in. Your agent can help you decide which approach fits the deal.

What does mitigation cost and involve?

The Walking Mountains guide gives these figures, which are national averages and older than today, so get local quotes:

• Installation: about $1,200 on average nationally
• Running cost: about $3 a month in Colorado
• Fan replacement: $145 to $300, roughly every 8 to 10 years
• Retest: every two years, and 24 hours to 30 days after installation to confirm the result is below 4 pCi/L

The guide also says that sealing cracks in the foundation alone is not an effective mitigation method. A standard system pulls air from beneath the slab and vents it above the roofline, with the fan outside the living space. Ask contractors for proof of certification, references, insurance and a written guarantee of results below 4 pCi/L.

What about radon in well water?

Radon in water is a lower risk and mostly affects homes on private wells. The Walking Mountains guide says about 10,000 pCi/L in water adds roughly 1 pCi/L to indoor air, and recommends testing indoor air first. If you are buying outside town on a well, see my guide to septic and wells in Gunnison County.

Is there help for lower-income homeowners?

CDPHE's radon page links to a Low Income Radon Mitigation Assistance (LIRMA) program. I did not verify current eligibility or funding, so call CDPHE at 303-692-2000 or check its website.

What is the bottom line?

Test every home you buy in Gunnison. A short-term test is quick, inexpensive compared with the purchase price, and gives you a number you can negotiate with. If the result is high, mitigation is a known, routine fix. A local agent can help you fold the test into your inspection timeline.

Frequently asked questions

Is Gunnison County in a high radon zone?

radonresources.com places Gunnison County in EPA Radon Zone 1, the highest-risk tier.

What radon level is too high?

The EPA action level is 4 pCi/L. At or above that, mitigation is recommended.

How long does a radon test take?

A short-term test takes about two to five days. Long-term tests run 91 days to a year.

Does the seller have to fix a high radon level?

No. Mitigation is negotiated between buyer and seller. Colorado sellers must disclose known radon, even if past results were under 4 pCi/L.

Connect with a great real estate agent in Gunnison, Kelsey Loftis with Crystal Peak Properties.

Phone: (970) 784-6768 · Email: kelseyloftis@gmail.com · Website: crystalpeakproperties.com

Sources: Colorado Department of Public Health and Environment, radon (cdphe.colorado.gov/radon); radonresources.com, Gunnison, CO radon page; Boulder County, "Radon and Real Estate Transactions in Colorado"; Walking Mountains, "Real Estate and Radon"; all reviewed November 4, 2026. The two guides are several years old, so confirm costs locally. Not medical or legal advice.