Radon Elimination System: What Mitigation Actually Does
A radon elimination system is what homeowners search for when they discover their home tests above the EPA action level and they want it gone. The technical truth is that radon cannot be eliminated. Radon is a naturally-occurring noble gas produced continuously by the radioactive decay of uranium and radium in soil. As long as the home sits on top of uranium-bearing soil (which is most homes in the United States and nearly all homes in the Front Range), radon will keep entering the building. This guide summarizes EPA and CDPHE guidance current as of 2026; consult a state-certified radon mitigation professional for testing and system design decisions. What homeowners can actually do is mitigate, which means reducing indoor concentration to acceptable levels through engineered systems. This guide explains how mitigation works, why “elimination” is the wrong frame, and what real-world systems achieve.
Why “elimination” is the wrong frame for radon
Radon is a decay product of uranium-238, which is present in trace amounts throughout the Earth’s crust. The Front Range sits on rock formations particularly rich in uranium, which is why the EPA Map of Radon Zones classifies all Colorado Front Range counties as Zone 1 (highest predicted radon levels). Uranium decays through several intermediate isotopes to radium-226, which decays to radon-222. The half-life of radium-226 is 1,600 years, so the radon supply in any given soil is effectively infinite on human timescales.
Radon enters the home through pressure-driven flow from the soil beneath the foundation. The stack effect of a heated home creates negative pressure relative to the soil, and soil gas (including radon) flows into the home through cracks, pipe penetrations, sumps, and porous foundation materials. Sealing every entry point is impossible because new cracks develop, materials are inherently porous to gas, and the pressure gradient continues to drive flow.
“Elimination” implies a one-time removal that permanently solves the problem. The radon situation is more like maintaining a sump pump: the system runs continuously to manage an ongoing input. Acknowledging this framing helps homeowners set realistic expectations and budget for ongoing operating costs. The parent radon testing guide covers the full mitigation framework.
What a real radon mitigation system actually does
The dominant residential mitigation approach is sub-slab depressurization (SSD). The system creates a region of low pressure under the concrete slab, which reverses the natural pressure-driven flow of soil gas into the home. Instead of soil gas leaking up through cracks into the basement, it flows toward a suction point under the slab and is vented to the atmosphere above the roof.
The components are simple. A 3-inch or 4-inch PVC pipe penetrates the basement slab. A small inline fan (typically 60 to 150 watts) creates continuous suction. The pipe runs from the suction point up through the home (or up the exterior wall) to a vent termination above the roof line. The system runs continuously, drawing soil gas from under the slab and venting it outdoors before it can enter the living space.
A properly-designed SSD system reduces indoor radon by 80 to 99 percent. A home that tests at 20 pCi/L pre-mitigation typically tests below 1.5 pCi/L post-mitigation. The remaining radon enters through pathways other than the soil under the slab (water, building materials, attached crawlspaces) and represents the practical floor for SSD-only mitigation. The radon mitigation techniques catalog covers the full menu of approaches.
System design choices that affect performance
Three design choices determine SSD performance. Suction-point location and quantity. Fan sizing and placement. Vent termination.
Suction point placement
The mitigation professional drills a 4-inch hole in the slab at a location that provides good pressure communication with the gravel or soil beneath. The standard approach is to drill near the center of the largest slab section. If the home has multiple slab sections separated by interior footings or expansion joints, additional suction points may be required. A home with one large basement plus an attached slab-on-grade garage may need two separate suction points and two separate fans.
Fan sizing and placement
Fan size depends on the sub-slab pressure communication. Loose gravel under the slab transmits suction efficiently and supports a small fan (60 to 90 watts). Tight compacted soil requires a larger fan (120 to 150 watts) to achieve adequate sub-slab vacuum. The professional measures sub-slab pressure during commissioning and selects the smallest fan that achieves the target.
Fan placement is constrained by safety. EPA requires the fan to be installed outside the conditioned living space (in the attic, on the exterior wall, or in the garage). A fan installed in the basement could vent radon-laden air into the home if the fan or its piping leaks.
Vent termination
The vent must terminate above the roof line, at least 10 feet from any window, door, or air intake, and at least 12 inches above the roof surface. Improper vent termination is one of the most common SSD installation errors and can lead to radon re-entry through nearby windows.
Cost expectations: $1,500 to $3,500
A standard SSD installation runs $1,500 to $3,500 in the Front Range market as of 2026. The price range reflects home complexity. Simple installations with a basement and direct exterior pipe routing fall toward the lower end. Complex installations requiring multiple suction points, internal pipe routing through finished spaces, or unusual vent terminations fall toward the upper end. The what-is-radon-mitigation guide breaks down related cost structures.
Operating costs are modest. The continuous fan draws 60 to 150 watts, costing $70 to $170 per year in electricity at $0.13/kWh. Fan lifespan is 5 to 10 years; replacement fans cost $100 to $250 plus installation. The total cost of ownership over 20 years is typically $4,000 to $7,000 including initial installation, electricity, and one or two fan replacements.
Post-mitigation testing and verification
Installing an SSD system is not the end of the mitigation process. The homeowner must verify the system actually achieves the target radon reduction through post-mitigation testing. The standard verification protocol uses a 48-to-90-hour short-term test with the SSD system operating in its normal mode (no extra ventilation, closed-house conditions). The result must show indoor radon below 4 pCi/L to count as successful mitigation.
Many state-certified professionals also include a long-term follow-up test (90+ days) to confirm the short-term result was representative. Some homes show seasonal variation, with winter radon levels slightly higher than summer levels due to stronger stack effect in cold weather. The long-term test captures both seasons and provides a more reliable picture of year-round performance.
The EPA radon program recommends re-testing every two years post-mitigation to confirm the system continues to perform. The CDPHE Colorado radon program tracks state-specific testing recommendations.
What happens when SSD does not achieve the target
About 5 to 15 percent of SSD installations do not achieve indoor radon below 4 pCi/L on the first try. Several causes are common. Insufficient sub-slab pressure communication (tight soil or extensive interior footings limiting suction reach). Untreated radon entry pathways (sumps not sealed, plumbing penetrations not caulked, crawlspace addition not addressed). Inadequate fan sizing.
Most state-certified mitigation professionals include a performance guarantee in their contract: if the post-mitigation test shows radon above 4 pCi/L, the professional returns to make adjustments at no extra cost. Adjustments may include adding a second suction point, upgrading to a larger fan, sealing previously-overlooked entry pathways, or adding supplemental ventilation. The combination of SSD plus HRV ventilation reliably handles even stubborn high-radon homes.
Front Range-specific factors
The Front Range housing stock has several characteristics that affect SSD design. Deep basements are common, which increases the surface area exposed to soil gas and the magnitude of stack-effect pressure differences. Tight new construction (especially homes built after 2010) reduces natural air infiltration and increases the stack-effect pressure. Many homes include radiant floor heating in the basement slab, which complicates suction-point drilling.
New construction in Boulder, Douglas, Jefferson, and El Paso counties often includes passive radon-resistant construction features per Appendix F of the International Residential Code. These features include a gas-permeable layer under the slab, vapor barrier, sealed pipe penetrations, and a vent stack from the sub-slab to the roof. Activating the passive system by adding a fan converts it to an active SSD system at significantly lower cost than a full retrofit.
Alternative and supplemental approaches
Several alternatives and supplements to SSD exist for specific home conditions. Sub-membrane depressurization (SMD) is the crawlspace equivalent of SSD. A heavy plastic membrane is laid over the crawlspace soil floor and sealed to the foundation walls. A fan draws air from beneath the membrane and vents it outdoors. SMD typically achieves the same 80 to 99 percent reduction as SSD on slab homes.
Drain-tile depressurization works on homes with perimeter drain tile systems around the foundation. The drain tile becomes the suction path instead of drilling a new hole in the slab. Drain-tile depressurization is sometimes the lowest-cost option when the existing drain system can be repurposed.
Block-wall depressurization addresses homes with hollow-core concrete block foundation walls. The hollow cores act as radon pathways from soil to interior. A fan-driven suction system applied to the wall cavity prevents soil gas from migrating through the wall. Block-wall systems are typically combined with SSD rather than used alone.
Water-borne radon is a separate issue in homes on well water. Granular activated carbon (GAC) filtration and aeration are the two primary water-radon mitigation technologies, depending on the source water concentration. Municipal water supplies have negligible radon and do not require water-side mitigation.
How to find a qualified mitigation professional
The Colorado Department of Public Health and Environment maintains a list of state-certified radon mitigation professionals. EPA recommends working with professionals certified through one of two national programs: the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB). Both programs require training, exam, and ongoing continuing education.
Three to five quotes from state-certified professionals is the typical bidding pattern for a homeowner project. Quotes should be within $500 to $800 of each other for similar scope; significantly low or high bids warrant follow-up questions. Front Range homeowners looking for a connection to a vetted state-certified mitigation professional can get in touch through our contact page.
The mitigation contract should specify the target post-mitigation indoor radon level (typically below 4 pCi/L), the post-mitigation testing protocol, the warranty period (typically 5 years on workmanship and 2 years on the fan), and the remediation procedure if the system fails to achieve the target. A handshake agreement on a $2,500 project is risky; a written contract protects both parties and clarifies expectations.
Ongoing maintenance to keep the system effective
SSD systems require minimal but non-zero maintenance. The fan is the wear component and lasts 5 to 10 years before requiring replacement. A simple U-tube manometer mounted on the pipe shows the system is creating suction; if the manometer reading drops to zero, the fan has failed and must be replaced. Most state-certified mitigation professionals install a manometer as part of the standard installation.
Annual checks should include verifying the manometer reading remains within the designed range, checking the vent termination above the roof for blockage by leaves or animals, and confirming the fan is operating quietly without unusual vibration. Re-testing every two years confirms the system continues to achieve the target reduction. The full maintenance burden is modest, but ignoring the system for 10 years can allow problems to develop unnoticed.
References
- EPA radon program — Environmental Protection Agency
- CDPHE Colorado radon program — Colorado Department of Public Health and Environment
- CDC radon health information — Centers for Disease Control and Prevention
- American Lung Association radon information — American Lung Association
Front Range homeowners considering radon mitigation can reach out through our contact page for a vetted state-certified mitigation referral.