High Radon Levels: What Front Range Homeowners Should Know
A radon result above the action threshold worries homeowners, and rightly so, because radon is the second-leading cause of lung cancer in the United States. But high radon levels are a solvable problem, not a reason to panic. Understanding what counts as high, why your home tested that way, and what to do next turns an alarming number into a clear plan. This guide summarizes EPA and Colorado state guidance current as of 2026; consult a certified radon professional for decisions specific to your home and a physician for health concerns.
What counts as high radon levels
Radon is measured in picocuries per liter of air (pCi/L). The EPA sets 4.0 pCi/L as the action level: at or above that, mitigation is recommended. Between 2 and 4 pCi/L, the EPA advises considering action, because no level of radon is entirely risk-free. Results in the high single digits or into the teens are common in radon-prone regions and warrant prompt attention.
For context, the average outdoor radon level is around 0.4 pCi/L, and the national indoor average is roughly 1.3 pCi/L. Many Colorado homes test well above both. The Front Range sits on uranium-bearing soils, and the Colorado Department of Public Health and Environment notes that a large share of homes statewide exceed the action level. The broader picture is laid out in the Colorado radon testing guide, and the health side is detailed in the explainer on how dangerous radon is.
Why Colorado homes test high
The geology and climate of the Front Range combine to drive radon indoors. Understanding the why helps homeowners take the result seriously without overreacting.
Geology
Radon comes from the natural breakdown of uranium in soil and rock. Colorado’s soils are relatively rich in uranium, so more radon gas is generated beneath homes than in many other states. The gas migrates upward through soil and enters through foundation cracks, sump pits, and slab penetrations.
Climate and construction
Cold winters mean homes stay sealed and heating systems run, creating a slight negative pressure that pulls soil gas indoors, an effect sometimes called the stack effect. Basements, common across the Front Range and often used as living space, sit closest to the source and tend to show the highest readings. These factors explain why a Colorado basement can read several times the national average.
The health risk behind the number
The concern with high radon levels is long-term, not acute. Radon and its decay products lodge in the lungs and emit radiation that damages lung tissue over years of exposure. The EPA attributes thousands of lung cancer deaths annually in the U.S. to radon, and the American Lung Association identifies it as the leading cause of lung cancer among people who have never smoked.
Risk rises with both the level and the years of exposure, and it multiplies sharply for smokers. A high reading does not mean immediate harm, but it does mean the home should be fixed so the cumulative exposure stops climbing. This is a measured response: test, confirm, mitigate.
How high radon levels enter a home
Knowing the entry routes makes a high reading less mysterious and points toward the fix. Radon gas migrates up through the soil and slips into a home wherever the foundation is not airtight, which is essentially everywhere a home meets the ground.
Common entry points
Cracks in concrete slabs and foundation walls, control and expansion joints, gaps around plumbing and electrical penetrations, sump pits, floor drains, and the porous surface of unsealed concrete all admit soil gas. Crawl spaces with exposed earth floors are particularly leaky. A home does not need a dramatic crack to test high; the cumulative effect of many small openings is enough.
The pressure that pulls it in
Homes operate at a slight negative pressure relative to the soil, driven by the stack effect, exhaust fans, and combustion appliances that draw indoor air. This pressure difference actively pulls radon from the ground into the lowest level. That is why simply sealing cracks rarely solves a high reading on its own; the home keeps pulling, and gas finds the next opening. A mitigation system works by reversing that dynamic beneath the slab.
What to do about high radon levels
If a short-term test reports a high level, confirm it. A follow-up test, ideally a long-term test over 90 days or a second short-term test, rules out a transient spike from weather. Once confirmed, mitigation is the fix. The proven method is active soil depressurization, in which a fan-driven pipe draws soil gas from beneath the foundation and vents it above the roofline, typically cutting indoor radon by 50 to 99 percent.
Use a certified radon mitigation professional, and re-test after installation to verify the system brought the level down. Sealing foundation cracks and the sump pit supports the system but is not a fix on its own. Homeowners weighing costs and approaches can review options in the guide to choosing a radon mitigation system. The path from a scary number to a safe home is well established, and most homes reach acceptable levels with a single properly installed system.
Living with results between tests
Radon levels are not fixed, so a high reading is best understood as a measurement of a moving target. Barometric pressure, wind, soil moisture, snow cover that caps the ground, and how a household runs its heating and ventilation all shift the indoor level day to day and season to season. A reading taken during a sealed-up January cold snap will often exceed a summer reading in the same home.
This variability has two practical consequences. First, a single high short-term result deserves confirmation before a homeowner commits to a fix, because it may capture a temporary peak. Second, once a system is installed and verified, periodic re-testing remains worthwhile, because soil conditions and home modifications can change performance over years. Finishing a basement, replacing a furnace, or repairing a foundation can all alter how radon enters and how the home holds it. Treating radon as an ongoing measurement rather than a one-time verdict is what keeps a household genuinely protected against the slow, cumulative risk the gas presents.
Testing to confirm a high level
Before acting on a high reading, it pays to understand how the number was produced, because the test type shapes how much confidence to place in it. A short-term test, running two to seven days, is quick but volatile; weather and how the home is operated during those few days can push a single result well above the true average. A storm, a cold snap that seals the house, or shifting barometric pressure can all skew a short window.
A long-term test, running more than 90 days, integrates those swings and reflects the year-round average far more reliably. For confirming a high short-term result, the strongest approach is either a long-term test or a second short-term test under controlled conditions. The placement matters too: tests belong in the lowest lived-in level, away from drafts, windows, and high humidity, following the protocol closely. A continuous radon monitor adds value by graphing hour-by-hour fluctuations, which reveals whether a high average came from a steady elevation or a brief spike, and helps rule out interference such as a window opened mid-test.
Mitigation and what to expect
Once a high level is confirmed, mitigation is a well-established fix, and knowing the process removes anxiety. The standard method, active soil depressurization, runs a sealed pipe from beneath the foundation to above the roofline with a continuously operating fan that draws soil gas out before it enters the home. A typical installation takes a single day for a standard house, and the system runs quietly in the background afterward.
Cost for a typical single-family system commonly falls between roughly $800 and $2,500, depending on foundation type and the complexity of the pipe routing, with ongoing electricity and eventual fan replacement as modest recurring costs. After installation, a post-mitigation test verifies the level dropped below the action threshold, and most homes reach acceptable levels with a single properly designed system. A manometer gauge on the pipe lets the homeowner confirm at a glance that the fan is working. For a Front Range homeowner, the path from an alarming reading to a safe home is routine and reliable, handled by certified professionals who do this work daily. Those weighing the financial side can review typical figures in the guide to radon mitigation system costs.
Putting a high reading in perspective
A high radon result understandably worries a homeowner, but context keeps the concern proportionate. The danger is a long-term, statistical increase in lung cancer risk, not an immediate threat to health, so a high reading calls for prompt action rather than panic. There is time to confirm the result and arrange mitigation properly; the cumulative risk accrues over years, not days.
It also helps to remember that radon is among the more solvable home hazards. Unlike some structural or environmental problems that defy clean resolution, an elevated radon level reliably responds to a proven, affordable mitigation system that typically cuts the level by 50 to 99 percent. The American Lung Association frames acting on an elevated result as a concrete, achievable step that meaningfully protects a household over the long run. For Colorado homeowners especially, where high readings are common, a confirmed high level is best seen not as bad luck but as useful information that points to a straightforward, lasting fix.
High radon levels and your family’s risk profile
The same radon level affects different households differently, which helps a homeowner gauge urgency. Smokers and former smokers face the steepest risk, because radon and tobacco smoke compound each other’s damage to lung tissue; the combination multiplies lung cancer risk well beyond either alone. Households with smokers therefore have the strongest reason to act promptly on a high reading.
Time spent in the home matters too. A finished basement used as a bedroom, home office, or playroom means occupants breathe the highest-radon air for many hours daily, raising cumulative exposure compared with a basement rarely entered. Children, who breathe faster relative to body size and have decades of future exposure ahead, are a particular consideration for families weighing a borderline result. None of these factors changes the fix, which remains a mitigation system, but they help a household decide how quickly to move and whether to mitigate a borderline level rather than wait. Understanding the personal risk profile turns a generic number into a decision tailored to the people actually living in the home.
Preventing high radon in new and remodeled homes
High radon is easier and cheaper to address when a home is being built or substantially remodeled, and Colorado homeowners undertaking such projects can build in protection. Radon-resistant new construction techniques, which the EPA promotes, install a gas-permeable layer beneath the slab, a plastic sheeting barrier, sealed openings, and a vent pipe routed from below the foundation to above the roof during construction. This passive system can later accept a fan if testing shows it is needed, at far lower cost than retrofitting from scratch.
For a major basement finish or foundation project, incorporating these features while the slab is accessible is a prudent step in a high-radon region. Even where local code does not mandate it, the modest added cost during construction is small compared with the value of a home built to resist the soil gas that the Front Range so readily produces. Homeowners planning new construction or a large remodel should discuss radon-resistant features with their builder early, and should still test the finished home, because no passive measure substitutes for a confirming test. Building prevention in from the start is the most cost-effective way to keep radon levels low over a home’s life.
References
- Health Risk of Radon — EPA
- Radon in Colorado — Colorado Department of Public Health and Environment
- Radon and Lung Health — American Lung Association
If your Front Range home tested above the action level, get in touch through our contact page to connect with a certified radon professional for confirmation testing and mitigation.