How Does a Radon Mitigation System Work?

On this page (7 sections)

1. How does a radon mitigation system work?
2. Do radon mitigation systems work?
3. How does a system lower radon in a crawl space or slab home?
4. How can you tell whether radon mitigation worked?
5. What can interfere with radon mitigation performance?
6. When should you call a radon professional?
7. What is the practical way to verify a radon system?

A radon mitigation system pulls soil gas from beneath or around a home and vents it outdoors, usually with a fan. A follow-up radon test checks whether the system lowered indoor levels.

The system does not destroy radon. Some systems rely on natural airflow instead of a fan; learn about passive radon mitigation.

It changes the path soil gas takes, so less enters the living space and more leaves through a vent pipe.

How does a radon mitigation system work?

A radon mitigation system works by creating suction at a collection point and routing soil gas through sealed piping to an outdoor exhaust. A fan often keeps the air moving, while sealed openings limit radon entry into the home.

Radon forms naturally in soil and rock. Pressure differences can draw it through foundation cracks, construction joints, sump openings, and gaps around pipes.

For a typical under-slab system, an installer places a pipe in a small pit beneath the concrete slab. The fan pulls gas from that point, then the pipe carries it upward and discharges it outdoors.

Some homes need a different collection method. A crawl space may use a membrane and suction beneath the barrier, while a home on a slab may need a collection point suited to its foundation and soil conditions.

Learn more about an under slab radon mitigation system when the home has a concrete foundation. A crawl space radon mitigation system uses a different approach to collect soil gas.

What does the fan do in a radon system?

The fan maintains a pressure difference that draws soil gas into the pipe. It sends that gas outside rather than letting it move through the foundation into rooms.

The fan is usually installed in a location that keeps the pipe under suction inside the home. That way, a leak in the indoor section is less likely to push radon into occupied areas.

The pipe's outlet needs to be positioned and installed to reduce the chance that exhaust re-enters through a window, door, or other opening. Follow the system design and local requirements rather than choosing an outlet location by appearance alone.

Do radon mitigation systems work?

Yes, radon mitigation systems can reduce indoor radon, but the amount depends on the home, the soil, the system design, and installation quality. Testing after the work is the way to check the result.

A system may draw gas from a limited area if the collection point or suction field doesn't reach the parts of the foundation where radon is entering. A professional may need to adjust the system or add another collection point if follow-up results remain high.

Radon levels can also vary over time with weather, ventilation, and building use. A single low reading after installation is useful evidence, but follow your local health authority's guidance on when to test again.

The EPA explains that a qualified radon professional can help identify the right mitigation method for a building. Review the agency's consumer guide to radon reduction for more on system approaches and testing after mitigation.

How does a system lower radon in a crawl space or slab home?

A system lowers radon by collecting soil gas close to where it enters the building. The collection surface and piping depend on whether the foundation is a slab, basement, or crawl space.

In a crawl space, a sealed ground membrane can help channel soil gas toward a suction point. The pipe and fan then exhaust it outdoors.

For a slab, suction may be applied beneath the concrete through a drilled opening and a small collection pit. If there is a basement, the same general principle can apply under the basement floor.

The right radon system design depends on the foundation, layout, and likely gas pathways. If you are comparing radon mitigation systems and their different types, focus on how each one collects and vents soil gas in your home's construction.

How can you tell whether radon mitigation worked?

You can tell whether mitigation worked by testing indoor radon after the system is operating and comparing the result with a reliable pre-installation measurement. The fan being on does not prove that indoor levels have fallen enough.

Use a test method suitable for the follow-up period and place it as instructed. Keep windows and doors closed as required by the test directions, and avoid placing the test near drafts or a vent.

The First Alert Radon Gas Test Kit includes test materials and lab fees, excluding New Jersey state fees. Results are emailed within 72 hours of lab receipt.

A test kit is useful for a measurement, but it does not monitor continuously or operate the mitigation fan. If the follow-up result is still raised, ask a qualified radon professional to inspect the system and recommend next steps.

What should you check on an active system?

Check the system indicator or manometer as the installer explains, and make sure the fan remains powered and running. A changed pressure reading, unusual fan noise, or loss of power can be a reason to contact the installer.

Don't treat a visible indicator as a substitute for a radon test. It can show that part of the system is operating, while only measurement checks the indoor result.

Radon is different from carbon monoxide, so a CO alarm cannot detect it. A radon monitor with an alarm system is designed for radon monitoring; the First Alert Plug in Carbon Monoxide Alarm is for CO safety.

What can interfere with radon mitigation performance?

System performance can suffer when the suction point doesn't reach the gas pathway, piping leaks, or the fan loses power. Changes to a foundation, crawl space, or home ventilation can also alter how air moves.

New cracks or openings can create additional entry paths. Keep access panels and sump covers in their intended condition, and don't block or alter the vent pipe without professional advice.

Water in a basement or sump area is a separate concern that can affect household equipment. The Basement Watchdog 110 dB Water Alarm has a detachable sensor with a 6 ft wire for placement in a sump pit or on a wall.

It does not measure radon or confirm that a mitigation system works. Treat water alarms, CO alarms, and radon tests as separate tools for separate risks.

When should you call a radon professional?

Call a qualified radon professional if post-installation testing remains high, the fan stops, or the system indicator changes. An installer can assess whether the design needs adjustment or the building needs another collection point.

A professional can also help when you are unsure which system fits your foundation or where an exhaust should end. See the guide to radon mitigation system installation for the steps and decisions involved.

A homeowner may be able to complete some simple maintenance, but system design and performance depend on the structure and soil. Read about a DIY radon remediation system before deciding whether a project is appropriate for your skills and home.

What is the practical way to verify a radon system?

To verify a radon system, keep it operating as designed and use a follow-up test to measure indoor levels. If the result is not satisfactory, get the system assessed and test again after any changes.

For a home on a slab, start with guidance for a radon mitigation system for a house on a slab. For other ways to address raised readings, see how to lower radon levels or how to reduce radon in a basement.

Sealant can be one part of certain radon work, but it isn't a substitute for a properly designed collection and vent system. The guide to Titebond gray radon sealant explains where that material may fit.

Choose the system for the home's foundation, then judge it by a follow-up radon test. A fan or indicator can show operation, while a test measures the indoor result.

Frequently asked questions

Do radon mitigation systems work?

Yes, a properly designed and installed radon mitigation system can lower indoor radon by drawing soil gas from beneath or around the home and venting it outside. The result needs to be checked with a radon test after installation, since performance depends on the building and system.

How does a radon mitigation fan work?

A radon mitigation fan creates suction in piping connected to a collection point under a slab, in a crawl space, or in another suitable area. The pressure change draws soil gas into the pipe and exhausts it outdoors, away from openings where it could re-enter.

How do I know if radon mitigation worked?

Use a radon test after the system is installed and operating, following the test instructions and any local guidance. Compare the result with the pre-mitigation measurement, and contact a qualified radon professional if levels remain raised or the system appears to have stopped working.

Does a radon system need electricity?

Many active soil-depressurization systems use an electric fan, so they need power to maintain suction. Check the installed system's indicator or manometer as directed by the installer, and arrange a retest if the fan stops or the pressure reading changes.