Radon has no color, odor or obvious warning sign. Testing turns an invisible question into a number buyers and sellers can address. This guide explains radon testing in Northern Colorado homes, including when to test, how to prepare, what the result means and where residents can find test kits.
This is general real-estate information, not medical, legal or environmental-testing advice. Follow the device instructions and use qualified radon professionals when a transaction or mitigation project calls for them.
Why Northern Colorado homes should be tested
Radon is a naturally occurring radioactive gas that can enter buildings from the ground. The Colorado Department of Public Health and Environment advises testing every home regardless of its geographic location or radon-zone designation. A neighborhood map, a neighbor’s result or the age of a house cannot tell you the concentration inside a specific property.
New construction is not automatically exempt. The EPA says new, old, tightly sealed and drafty homes—with or without basements—can have elevated radon. When evaluating a newly built home, ask whether radon-resistant construction features were installed and whether the completed home was tested. The EPA still recommends testing even when those features are present.
For a buyer, a radon test can be part of the inspection plan. For a seller, testing before listing may create more time to review the result, gather estimates and address an elevated level.
Build the test into the transaction schedule
The EPA’s current Home Buyer’s and Seller’s Guide to Radon says buyers and sellers should have the home tested. A short-term test can provide a faster answer for a real-estate transaction, but all radon measurements need enough time and proper conditions to be meaningful.
EPA guidance says tests should run for at least 48 hours, although the specific device may require longer. The test is generally placed in the lowest level that could be used regularly, not simply wherever it is most convenient. Closed-building conditions, correct placement and protection from interference matter. Follow the test provider’s instructions instead of moving the device, opening windows for ventilation or changing normal operation of the home during the test.
Ask early who will order the test, who will have access to the report and how the dates fit the inspection and objection deadlines. Contract rights and deadlines vary, so buyers and sellers should rely on their signed agreement and professional advisers rather than assuming every transaction handles radon the same way.
If you are organizing a purchase, the Northern Colorado buyer resources page is a useful starting point. Sellers can use the seller resources page to think through preparation, documentation and timing before the property reaches the market.
What a radon result means
Radon in air is commonly reported in picocuries per liter, abbreviated pCi/L. The EPA action-level guidance recommends fixing a home when the result is 4 pCi/L or higher. Because no level of radon exposure is known to be risk-free, EPA also recommends considering a reduction when the result is between 2 and 4 pCi/L.
A number near the action level deserves careful interpretation. The EPA buyer-and-seller guide explains that radon levels vary by day and season and that a longer test is more representative of the year-round average. In a time-limited transaction, the report, testing method and applicable follow-up recommendation should be reviewed with the tester and the parties’ advisers.
An elevated result does not mean the sale must end. Buyers and sellers can discuss timing, access and cost when mitigation becomes part of a transaction. The scope should come from a qualified radon professional.
What sellers should save and share
Keep the complete radon report, test dates, device or laboratory information, mitigation proposal, installation documents and any post-mitigation test results together. If the home already has a mitigation system, keep service information and clearly identify the system components for inspectors and future owners.
The EPA’s retesting guidance notes that a buyer may request a new test when an earlier test is not recent, when the home has been renovated or altered, when testing conditions were not followed, or when the buyer expects to occupy a lower level that was not previously tested. An old report can still be useful history, but it may not answer the current question.
Do not remove, conceal or casually disable a mitigation system before listing. If a fan, alarm or pipe configuration appears questionable, have the system evaluated and document what was repaired.
Where to find test kits in Larimer and Weld counties
Colorado’s radon FAQ says the state offers one free test kit per household per year while supplies last. Availability can change, so use the current order form rather than assuming a kit is in stock.
Larimer County’s radon resource page links residents to state kits, discounted Fort Collins kits and retail or online options. The county also recommends retesting after major renovations or ventilation changes and periodically checking a home with an existing mitigation system.
The Weld County radon page provides local testing and mitigation information. Weld County’s current air-quality program says free short-term kits are offered to county residents, one per household, while supplies last. Confirm availability before making a trip or relying on that option for a contract deadline.
Radon testing FAQ
Can I rely on a neighbor’s radon result?
No. Radon levels can differ from one home to the next. Test the specific property rather than inferring a result from a subdivision, map or nearby house.
Should a home with a mitigation system be retested?
Yes. Retesting verifies how the system is performing. Larimer County’s 2026 guidance recommends retesting a mitigated home every two years, and testing again after major renovations or changes to ventilation is also prudent.
Does a passive radon pipe in new construction mean the problem is solved?
Not necessarily. Ask what components were installed, whether the system is passive or fan-activated, and whether the finished home was tested. EPA recommends testing after occupancy even when radon-resistant features were built in.
How can Brandon help?
Brandon can help buyers and sellers plan the real-estate timeline, request documentation and coordinate the conversation among inspectors, contractors and the other party. For testing protocols, health questions and system design, rely on the appropriate qualified professionals. Contact Brandon to discuss a Northern Colorado purchase or sale.