How to Mitigate Radon: A Plain-Language Guide
Radon is the leading environmental cause of lung cancer among non-smokers, and Colorado’s Front Range sits in one of the highest-radon regions in the country. The encouraging news is that radon is fixable: proven mitigation methods can drop indoor levels by 80 to 99 percent. Knowing how to mitigate radon — and which method fits your home — helps you act decisively after a high test result. This guide summarizes EPA and Colorado Department of Public Health and Environment guidance current as of 2026; confirm levels with testing and hire a certified mitigation professional for installation.
How to Mitigate Radon: The Short Answer
The most effective and common way to mitigate radon is active sub-slab depressurization (ASD): a fan-driven system that draws radon-laden air from beneath the foundation and vents it safely above the roofline before it can enter the home. For most houses with a basement or slab, this single approach reliably brings levels below the EPA action threshold of 4.0 picocuries per liter (pCi/L). Sealing cracks, improving ventilation, and pressurization play supporting roles, but ASD is the workhorse of radon reduction.
Mitigation only makes sense after testing confirms a problem. The EPA recommends fixing homes at or above 4.0 pCi/L and considering action between 2.0 and 4.0 pCi/L. Colorado homeowners can review the broader context of radon testing for Front Range homes before deciding to mitigate.
Why Radon Concentrates Along the Front Range
Radon forms from the natural decay of uranium in soil and rock, then seeps into homes through foundation cracks, sump pits, and slab penetrations. Colorado’s geology is uranium-rich, and the EPA places nearly all Front Range counties — Denver, Boulder, Jefferson, Douglas, El Paso, Arapahoe, and others — in Zone 1, the highest radon potential category. The CDPHE reports that roughly half of Colorado homes tested exceed the EPA action level, far above the national average.
Because the gas is colorless and odorless, testing is the only way to know. Homeowners curious about where the gas originates can read the explainer on where radon gas comes from for the underlying geology.
The Main Radon Mitigation Methods
Active sub-slab depressurization (ASD)
The gold standard. A PVC pipe is inserted through the slab into the soil or aggregate beneath. An inline fan creates suction that intercepts radon and vents it above the roof. ASD works on basements, slab-on-grade, and many crawl-space homes. It is the method most certified contractors install first because of its reliability. The mechanics are detailed in the guide on how a radon mitigation system works.
Sub-membrane depressurization
For homes with a dirt-floor crawl space, a sealed plastic membrane is laid over the soil and a fan draws radon from beneath it. This is the crawl-space equivalent of ASD.
Sealing and caulking
Sealing foundation cracks, the sump pit, and slab penetrations reduces entry routes. On its own, sealing rarely solves a radon problem, but it improves the efficiency of an active system and is a standard part of installation.
Ventilation and pressurization
Increasing ventilation or pressurizing the basement can dilute or push back radon, but these approaches are less reliable and can raise energy costs in Colorado’s cold winters. They are generally secondary to ASD.
What Radon Mitigation Costs
A professionally installed active system in Colorado typically costs $800 to $2,500, with most Front Range homes falling between $1,000 and $1,800. Cost depends on the foundation type, the number of suction points needed, fan size, and how the system is routed and finished.
- Standard basement ASD: $1,000 to $1,800
- Multiple suction points or complex layouts: $1,800 to $2,500+
- Crawl-space sub-membrane systems: often at the higher end
- Ongoing fan electricity: roughly $5 to $15 per month
Homeowners comparing quotes can review typical pricing in the guide on radon mitigation system costs to set expectations before hiring.
Step-by-Step: How Mitigation Happens
- Test first: Confirm elevated levels with a short-term or long-term test placed in the lowest lived-in level.
- Diagnostic assessment: A certified contractor evaluates the foundation, locates suction points, and plans the routing.
- Install the suction point: Core a hole through the slab and connect PVC piping into the soil or aggregate.
- Route the pipe and fan: Run piping to an inline fan, then vent above the roofline away from windows.
- Seal entry points: Caulk cracks, the sump pit, and penetrations to boost efficiency.
- Add a monitor: Install a manometer (U-tube gauge) so the homeowner can confirm the fan is working.
- Re-test: Test again after 24 hours to several weeks to verify the system brought levels below 4.0 pCi/L.
The installation sequence is described in detail in the guide on how to install a radon mitigation system.
Verifying the System Works
Mitigation is not finished until a post-installation test confirms success. A good system routinely brings levels well below the action threshold, often under 2.0 pCi/L. The manometer offers an at-a-glance check: if the colored liquid levels equalize, the fan has likely failed and needs service.
Radon levels also fluctuate seasonally, peaking in winter when homes are sealed against the cold — a real factor in Colorado. The EPA recommends re-testing every two years and after any major renovation or foundation work, even with a system running.
Mitigating Different Foundation Types
The right approach depends heavily on how the home sits on the ground, and the Front Range has a mix of all of them.
Full basement
The most common and most straightforward case. A single suction point cored through the basement slab, connected to a properly sized fan, usually handles the entire home. Denver-area split-levels and ranch homes with full basements typically need just one suction point unless the slab is divided by interior footings that block airflow.
Slab-on-grade
Homes built directly on a concrete slab without a basement still benefit from sub-slab depressurization, with the suction point cored through the slab into the gravel or soil beneath. Routing the pipe is sometimes trickier because there is no basement to conceal it, so installers often run piping through a closet, garage, or up an exterior wall.
Crawl space
Dirt-floor crawl spaces use sub-membrane depressurization: a heavy polyethylene sheet is sealed over the soil, and the fan draws radon from the space beneath it. This requires careful sealing of the membrane seams and edges. Mixed foundations — part basement, part crawl space — may need multiple suction points or a combined system.
Homes with multiple slabs or additions
Older Front Range homes that grew through additions often have disconnected slab sections. Each isolated slab area may need its own suction point because airflow does not cross the footings between them. A diagnostic smoke or pressure-field test guides how many points are required.
Common Mitigation Mistakes to Avoid
Even well-intentioned projects fail when key details are overlooked. The recurring errors include:
- Skipping the diagnostic: Installing a system without measuring sub-slab pressure communication can leave dead zones where radon still enters.
- Venting too low or near windows: The exhaust must clear the roofline and stay away from openings, or radon can re-enter the home.
- Mismatched fan capacity: A fan too weak for tight Colorado clay soils will not pull enough suction; an oversized fan wastes energy and pulls heated air out of the home.
- Neglecting to seal: Leaving the sump pit uncovered or cracks unsealed lets the fan pull conditioned house air instead of soil gas.
- No post-installation test: Because radon is invisible, the only proof of success is a follow-up test. A system that looks finished can still fail silently.
Avoiding these mistakes is the difference between a system that merely runs and one that actually protects the household.
What to Expect After Installation
Once a system is in place, homeowners should notice almost nothing day to day. A well-installed fan produces a faint hum, and the manometer gauge sits with offset liquid columns showing active suction. The system runs continuously and requires little maintenance beyond an occasional glance at the gauge and periodic re-testing.
Some homeowners report a slight reduction in basement humidity and musty odors, a side benefit of drawing soil gas and moisture out from under the slab. Energy impact is small, roughly the cost of running a standard light bulb continuously, plus any minor heated-air loss. Most Colorado homeowners find the trade-off easily worthwhile given the health stakes, and the system adds resale value because radon disclosure is standard in the state’s real estate transactions.
When to Call a Professional
While determined DIYers can install systems, certified professionals bring diagnostic skill, proper fan sizing, code-compliant venting, and post-installation verification that the system actually works. In a Zone 1 region like the Front Range, where high results are common and stakes are real, professional installation is usually the safer investment. Look for contractors certified through a recognized radon proficiency program, and ask for a guaranteed post-mitigation level — reputable installers will commit to bringing the home below 4.0 pCi/L.
A professional installation also typically comes with a workmanship warranty and a guarantee on the post-mitigation radon level, protections a DIY job cannot offer. For homes with complex foundations, multiple suction points, or a history of stubbornly high readings, the diagnostic expertise alone usually justifies the cost. Acting on a high test result is one of the most cost-effective health investments a Colorado homeowner can make, and pairing that action with verified results ensures the money spent actually buys lower radon.
Passive vs. Active Systems
Not every radon system uses a fan. Many newer Colorado homes are built with a passive radon system: a vent pipe running from beneath the slab up through the roof, relying on natural air movement (the stack effect) to draw radon out without powered assistance. Passive systems are cheaper to install during construction and sometimes lower radon enough on their own.
The catch is reliability. Passive systems often fail to bring high readings below the action level, especially in colder months. The common fix is straightforward: add an inline fan to the existing pipe, converting it to an active system. Because the rough-in is already in place, this conversion is usually inexpensive — often just the cost of the fan, wiring, and a re-test. Homeowners buying a house with a passive system should test it; if levels are still elevated, activating it is typically a quick and affordable upgrade rather than a full installation.
Maintaining a Radon System Long-Term
A mitigation system is not entirely set-and-forget. The fan runs continuously and will eventually wear out, typically after 5 to 10 years, so it is a serviceable component rather than a permanent fixture. Routine maintenance is minimal but worth the small effort.
The key habits are checking the manometer gauge periodically — equalized liquid columns signal a failed fan — listening for changes in the fan’s sound, and re-testing radon every two years as the EPA recommends. When the fan fails, radon levels climb again, so prompt replacement matters. Homeowners should also avoid blocking or altering the system: covering the vent, disconnecting the fan to save electricity, or sealing it off defeats the purpose and quietly restores the hazard. Treating the system as a working safety device, like a smoke detector, keeps it protecting the household for the long haul across the occasional fan replacement.
References
- Consumer’s guide to radon reduction — U.S. Environmental Protection Agency
- Radon information for Colorado homeowners — Colorado Department of Public Health and Environment
- Radon and lung health — American Lung Association
Front Range homeowners with a high radon result can get in touch through our contact page to connect with a vetted local professional for testing and certified mitigation.