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Radon Mitigation System

A radon mitigation system pulls radon-rich air from beneath your home and vents it safely outdoors. When it’s designed right, it lowers indoor radon fast, runs quietly, and needs very little attention. This guide breaks down how systems work, what “good” installation looks like, what it costs in Missouri, and how to keep performance steady year after year.

Radon is a naturally occurring radioactive gas that comes from soil and rock. You can’t see or smell it, and it can build up indoors through small gaps in foundations, sump lids, floor joints, and utility penetrations. Over time, breathing elevated radon increases lung cancer risk.

If you’ve tested at or above the EPA action level of 4.0 pCi/L, mitigation is the standard next step. Many homeowners also choose to reduce radon when results land between 2.0 and 4.0 pCi/L, especially if they spend lots of time in the basement.

How a radon mitigation system actually works

Most homes use active soil depressurization (ASD). In plain terms, the system creates a mild vacuum under the slab or under a crawl space liner, then moves that air through a pipe to a fan and up above the roofline where it disperses. This keeps radon from entering living space.

A typical setup has a few core parts:

A suction point (often a small pit under the slab, or a connection to a sump crock)
PVC vent piping that routes suction to a discharge point
A radon fan (usually mounted outside the living area, commonly in an attic, garage, or exterior)
A system monitor, often a U-tube manometer that shows pressure difference
Optional sealing, which supports performance but usually isn’t the main fix

The fan’s job isn’t to “filter” radon. It’s to redirect air flow so radon doesn’t drift inside. That’s why good pipe routing, solid joints, and the right suction strategy matter more than fancy add-ons.

What “good installation” looks like in real homes

Homes are not one-size-fits-all. A 1950s slab with a basement, a newer home with drain tile, and a split-level with a crawl space can each need a different approach. A strong design usually includes:

1) Smart suction placement
The goal is even sub-slab communication, meaning the vacuum reaches enough of the footprint to capture radon before it gets indoors.

2) Proper discharge location
Exhaust should vent above the roofline and away from openings so discharged air doesn’t re-enter through a window, soffit, or attic vent.

3) Fan placement that avoids indoor leaks
Fans are ideally outside the conditioned space. If a joint leaks after the fan and it’s inside your home, that leak can push radon into the house instead of out.

4) Quiet, stable performance
A properly matched fan and well-supported pipe run reduces vibration noise. Systems can be very quiet when they’re planned and secured well.

Costs and what drives the price

In Missouri, state guidance commonly cites mitigation costs that are often $2,000 or less for a typical home size, though real-world pricing can vary with foundation style, pipe routing complexity, and electrical needs.

Price tends to move based on:

Number of suction points needed
Finished basement constraints (routing is harder when walls are closed in)
Crawl space size and whether a full liner and sealing is required
Electrical distance to the fan location
Whether a sump needs a sealed lid

Did You Know? Basement “smell” isn’t a radon clue

Many people link musty odor to radon. Radon has no smell. A basement can smell fine and test high. Or smell damp and test low. That’s why testing is the only way to know.

Keeping your system working

Radon systems aren’t high-maintenance, but they aren’t “set it and forget it” forever.

Practical upkeep:

Look at the manometer once a month. If the levels look different than usual, it may signal a fan issue or a pipe problem.
Re-test radon every couple years, and after big changes like new HVAC, finishing a basement, or foundation work.
If the fan fails, replace it promptly. Most systems drop performance quickly without active suction.

Common Questions Around Radon Mitigation System

What radon level means I need a mitigation system?
EPA recommends fixing the home at 4.0 pCi/L or higher. Many people also reduce levels between 2.0 and 4.0 pCi/L when it’s practical.

How long does installation take?
Many single-system installs are completed in a day, but routing and crawl space work can extend timelines.

Will mitigation make my home too dry or increase heating bills?
A standard ASD system moves air from beneath the slab, not large volumes of conditioned indoor air. Energy impact is usually modest, though every home is different.

Do I still need to test if I have a system?
Yes. Fans wear out, remodels change air movement, and seals can fail. Periodic testing is the only proof of performance.

Can I install a system myself?
Some homeowners attempt DIY, but professional design reduces the chance of poor suction, bad discharge placement, or indoor leakage. EPA guidance emphasizes qualified pros for mitigation work.

Related Terms
Radon fan, sub-slab depressurization, sump lid sealing, crawl space liner, radon manometer

Additional Resources

Expand Your Knowledge
Learn the health background at https://www.cancer.gov/about-cancer/causes-prevention/risk/substances/radon/radon-fact-sheet.
See Missouri’s radon program guidance at https://health.mo.gov/living/environment/radon/index.php.
Explore radon mapping data at https://www.usgs.gov/data/geologic-radon-potential-map-united-states.

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