How Radon Mitigation Works

The method: sub-slab depressurization

Radon enters your home because the air pressure inside is slightly lower than in the soil beneath it, so soil gas gets drawn in. A sub-slab depressurization system reverses that: a fan creates a gentle suction under the basement floor and vents the radon outdoors before it can get inside. Health Canada identifies this as the most common and effective way to reduce radon.

What happens on installation day

1. Diagnostic testing. The installer drills small test holes and measures how well air moves under the slab. This decides where the suction point goes and how strong the fan needs to be.
2. Suction point. A hole of a few inches is cored through the basement floor and some soil is removed beneath it to create a small pit.
3. Piping. A sealed PVC pipe runs from the suction point to the outside, usually through a rim joist, garage or exterior wall.
4. Fan. An in-line radon fan is mounted outside the living space, for example in the garage, attic or on an exterior wall.
5. Exhaust. The pipe discharges above the roofline, away from windows and doors, where radon quickly disperses.
6. Sealing. Sump pit lids, floor drains and major cracks are sealed to make the system more effective.
7. Gauge and labels. A simple pressure gauge on the pipe lets you check at a glance that the system is running.

Most installations are completed in less than a day.

After installation: retest

Health Canada recommends a follow-up long-term test after a system is installed to confirm radon is below the guideline. A good installer will help you arrange this.

What about sealing or ventilation alone?

Sealing cracks and increasing ventilation, for example with a heat recovery ventilator (HRV), can help, but on their own they usually reduce radon far less than a sub-slab system. Air purifiers are not a recognized way to lower radon gas. For homes above the guideline, Health Canada recommends a certified professional assess the best solution.