Radon, Recessed Lighting, and Why Denver Homes Age You

By Franklin Everett Shaw

March 12, 2026

Is your Denver dream home slowly poisoning you? It sounds dramatic, but the silent threat of radon gas is a serious concern for homeowners in the Mile High City. Denver’s unique geology, coupled with common architectural features, creates a perfect storm for elevated radon levels. Let’s dive into why Denver is particularly vulnerable and, more importantly, what you can do about it.

Denver sits atop the Colorado Piedmont, a geological region rich in uranium. Uranium decays into radium, which in turn decays into radon, a colorless, odorless, and tasteless radioactive gas. This naturally occurring process means that radon is present in the soil throughout Colorado, but certain areas, like Denver, have significantly higher concentrations.

Older homes in Denver, particularly those built before radon mitigation became standard practice, are especially susceptible. These homes often feature basements, which act as natural collection points for radon seeping up from the ground. But there’s another, often overlooked culprit: recessed lighting.

Recessed lighting, a popular design choice in many Denver homes, creates pathways for radon to enter living spaces. The gaps around the fixtures in the ceiling allow radon gas from the attic or spaces between floors to flow directly into the rooms below. This is especially problematic in older homes where the seals around these fixtures may have deteriorated over time.

So, how do you know if your Denver home has a radon problem? Testing is the only way to be sure. Fortunately, it’s a relatively simple and inexpensive process.

Here’s a step-by-step guide to testing for radon in your Denver home:

Choose a Testing Method: You have two main options: a short-term test kit or a long-term test kit. Short-term kits provide results in 2-7 days, while long-term kits measure radon levels over 90 days or more, providing a more accurate annual average. For an initial assessment, a short-term test is usually sufficient. You can purchase these kits at most hardware stores in Denver, or online. Look for kits certified by the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB).
Prepare Your Home: Close all windows and exterior doors for at least 12 hours before starting the test. This helps to ensure an accurate reading. Avoid running fans or using fireplaces during the test period, as these can affect air circulation.
Place the Test Kit: Follow the instructions included with your test kit carefully. Generally, you’ll place the kit in the lowest livable area of your home, such as the basement or first floor. Keep the kit away from drafts, direct sunlight, and exterior walls.
Wait and Send: Leave the test kit in place for the recommended duration (usually 2-7 days for short-term tests). Once the testing period is complete, seal the kit according to the instructions and mail it to the lab for analysis.
Interpret the Results: You’ll receive a report from the lab indicating the radon level in your home, measured in picocuries per liter (pCi/L). The EPA recommends taking action to mitigate radon if the level is 4 pCi/L or higher. Colorado’s Department of Public Health and Environment (CDPHE) also follows this guideline.

Now, let’s talk about those recessed lights. If your radon test reveals elevated levels, sealing these fixtures can make a significant difference.

Here’s how to seal recessed lighting fixtures to reduce radon entry:

Turn Off the Power: Safety first! Disconnect the power to the circuit that controls the recessed lights.
Remove the Trim: Carefully remove the trim ring or baffle from the recessed light fixture.
Seal the Gaps: Use a high-quality, fire-resistant caulk to seal any gaps between the fixture housing and the ceiling drywall. Pay close attention to the area where the electrical wires enter the fixture.
Install a Recessed Light Cover: Consider installing a pre-made recessed light cover. These covers are designed to create an airtight seal around the fixture, preventing radon from entering the living space. You can find these covers at most home improvement stores.
Replace the Trim: Once the caulk has dried and the cover (if used) is in place, replace the trim ring or baffle.
Restore Power: Turn the power back on to the circuit.

It’s important to note that sealing recessed lighting is just one step in radon mitigation. If your radon levels are significantly elevated (above 4 pCi/L), you’ll likely need to install a radon mitigation system.

Radon mitigation systems typically involve installing a vent pipe and fan to draw radon gas from beneath the foundation and exhaust it safely outside. These systems are usually installed by certified radon mitigation professionals. The CDPHE maintains a list of certified radon mitigation professionals in Colorado.

One common mistake Denver homeowners make is relying solely on DIY radon mitigation efforts when professional help is needed. While sealing recessed lighting and other minor fixes can help, they are often insufficient to address high radon levels. Another pitfall is failing to retest after mitigation. Retesting is crucial to ensure that the mitigation system is working effectively and that radon levels have been reduced to an acceptable level.

Consider the case of a homeowner in the Washington Park neighborhood of Denver. They tested their home and found radon levels of 8 pCi/L. They attempted to seal the recessed lighting and other potential entry points themselves, but retesting revealed that the radon levels had only decreased to 6 pCi/L. They then hired a certified radon mitigation professional who installed a sub-slab depressurization system. Retesting after the installation showed that radon levels had dropped to below 1 pCi/L.

Radon is a serious health risk, but it’s also a manageable one. By understanding the unique challenges Denver homeowners face, testing your home, and taking appropriate mitigation steps, you can protect your family from the dangers of radon exposure. Don’t let the silent threat of radon compromise your health and the value of your Denver home. Take action today.