A note before you read. This is general information for Canadian homeowners — not medical, legal, financial, or warranty advice. Radon results are reported against Health Canada's guideline of 200 Bq/m³. RadonTest.ca coordinates test-kit logistics and sample submission only; we do not interpret your results, assess your health, or design, inspect, or service mitigation systems. All analysis is performed independently by a Canadian C-NRPP-certified laboratory. For advice on your specific system, consult a C-NRPP-certified mitigation professional, and use a licensed electrician for any wiring.
Quick answer
The radon fan is the active heart of an active soil depressurization (ASD) system — the most common way to lower radon in a Canadian home. It runs continuously, 24 hours a day, drawing soil gas from beneath your foundation slab and pushing it up a sealed vent pipe to discharge safely outdoors, where it disperses within a few feet. Key facts: in Canada the exhaust is usually a sidewall discharge — out through an exterior wall, above grade, with set clearances from windows, doors, and air intakes — while a roof discharge is also code-compliant but is used mainly when sidewall clearances can't be met; the fan sits on the pressure side of the system, so it is placed so that pressurized pipe never runs through finished, occupied rooms (in Canada it is commonly mounted indoors — an unfinished basement or mechanical room — thanks to sealed, radon-specific fans); the U-tube manometer on the pipe shows the fan is running, not what your radon level is; it is a small, continuous electrical load; and it eventually wears out and needs replacement. After any install or repair, a long-term test of at least 91 days is the only way to confirm your home is back below 200 Bq/m³.
What a radon fan actually does
Radon is a soil gas. It seeps up from the ground and is drawn into a home through cracks, the floor–wall joint, service penetrations, and openings like sump pits. An ASD system reverses that pathway: a pipe is connected to the gravel or soil under your slab, and a fan on that pipe creates a small, constant zone of suction beneath the foundation. Instead of drifting up into your basement, the soil gas takes the path of least resistance — into the pipe and out above the roof. For how the whole system fits together, see how radon mitigation works.
The fan is what makes the system active: without it, you have a pipe and no suction. It is the single moving part that keeps everything working. According to Health Canada, a properly designed and installed active system reduces radon by more than 80% in most homes, often bringing levels close to what you would measure in outdoor air.
Why the fan must run 24/7
A common question is whether the fan can be switched off at night or in summer to save power. The answer is no. Soil gas is produced continuously, and the negative-pressure field under your slab only exists while the fan runs. Turn it off and, within hours, the suction disappears and radon can climb back toward its pre-mitigation level. The fan is built for continuous duty, and leaving it on is exactly how it is meant to be used. That is also why it is wired to run on its own, not on a switch. If you ever find it unplugged or a breaker tripped, treat it as urgent — the system is not protecting you while it is off.
The vent pipe: where the radon goes
The vent pipe (the radon vent pipe or exhaust stack) carries collected soil gas from under the slab up and out of the building. Canada's national mitigation standard, CAN/CGSB-149.12, sets where that pipe can end: the discharge point must clear openable windows, doors, and fresh-air intakes so the gas disperses before it can re-enter your home or a neighbour's. (A Health Canada field study found radon falls back to normal outdoor levels within a few feet of the discharge point.) In Canada, that termination is most often a sidewall discharge — the pipe passes through an exterior wall and ends above grade at the required clearances. Sidewall discharge is fully code-compliant and is usually the preferred choice here: it is more energy-efficient, easier to inspect and service, and keeps the fan out of harsh rooftop weather. A through-the-roof (roofline) discharge is also compliant, but it is generally reserved for cases where sidewall clearances can't be met. So if most systems you see run out through the wall and vent at the side of the house rather than up past the roof, that is normal, expected, and code-compliant — not a shortcut. Everything from the fan upward is on the pressure side of the system, which is why the fan's placement matters.
Where the fan is mounted — and why placement matters
The pipe after the fan is under slight positive pressure. If it leaked inside a finished room, it could push radon-laden air into the living space. So the rule isn't "keep the fan outside the house" — it's that the fan and the pressurized pipe are kept out of finished, occupied areas, so any leak stays clear of the breathing zone.
This is where Canadian practice differs from the older U.S. convention. With today's sealed, radon-specific fans built for cold climates, Canadian installers commonly mount the fan indoors — in an unfinished basement, a mechanical or utility room, or the attic — as well as in a garage or outdoors. Keeping the fan inside protects it from freezing and makes service easier, and the sealed system keeps the pressure side from leaking into living space.
| Common, compliant fan locations | Locations to avoid |
|---|---|
| Unfinished basement or mechanical/utility room (common in Canada) | Inside a finished, occupied room |
| Attic above the ceiling, garage, or outdoors | A bedroom, family room, or living area |
| Any unoccupied space where the sealed pressure pipe won't leak into living areas | Anywhere the pressurized pipe runs through occupied space |
A C-NRPP-certified installer chooses the fan location, size, and pipe route — and the discharge point — from diagnostic testing of your specific home.
The U-tube manometer shows the fan — not your radon level
Somewhere on the pipe you will see a small clear U-shaped tube, partly filled with coloured liquid: the manometer, and it is widely misunderstood. When the fan runs, it creates a pressure difference that pushes the two liquid columns to different heights. Uneven columns mean the fan is pulling suction; level (equal) columns mean the fan has stopped or the system has lost pressure — a signal to investigate.
The crucial part: the manometer measures pressure in the pipe, not radon in your air. It cannot tell you whether your home is above or below 200 Bq/m³. A system can show a healthy reading and still, in rare cases, underperform on radon — which is why measurement is separate from the gauge. For the full explanation, see is my radon mitigation system working?.
What a radon fan costs to run
Because the fan runs continuously, homeowners reasonably ask about electricity. A residential radon fan is a small, steady load — think of a single lightbulb left on around the clock rather than a furnace or air conditioner. Draw varies by model and by how hard the system has to work; the figure for your fan is on its rating plate, and your installer can confirm it. Running 24/7, that adds a modest, predictable amount to a monthly bill; the exact cost depends on the fan and your local electricity rate. It is best seen as a small ongoing operating cost of keeping radon out. For how this fits alongside the up-front price of a system, see radon mitigation cost in Canada.
Noise: what's normal and what isn't
A well-installed radon fan produces a low, steady hum — mostly the sound of moving air — and in most homes it fades into the background, especially since it sits in an unoccupied space, away from where you spend time. What is not normal is a new rattle, grinding, or buzz, or a noticeable increase in vibration. Those usually point to worn bearings, a loose mount, or debris, and often mean a fan is nearing the end of its life. Vibration-damping couplings and a solid mount keep sound down; if the noise suddenly changes, have the system looked at rather than tuning it out.
Fan lifespan and replacement
Radon fans are built for continuous operation but are still mechanical devices with a finite life. Manufacturers publish a warranty period for each model, and a fan eventually wears out when the motor or bearings give up.
| Sign | What it may mean | What to do |
|---|---|---|
| Manometer columns now level/equal | Fan has stopped or lost pressure | Check power; call a mitigation pro if it won't restart |
| New grinding, rattling, or louder hum | Worn bearings; fan aging | Plan for inspection/replacement |
| Radon retest has crept back up | Reduced fan performance or a new leak | Have the system diagnosed and retest |
When a fan is replaced, the new unit should match the system's design, so a C-NRPP professional confirms the correct size. And this is not a casual DIY electrical project: wiring must meet code, the fan and pressurized pipe must stay out of finished, occupied space, and sizing depends on diagnostics. Leave installation and replacement to a mitigation professional, with any wiring done by a licensed electrician where required.
Confirm the fix with a long-term test
Installing or replacing a fan is only half the job — the other half is proving it worked. A short-term test at start-up can confirm the fan is doing something, but radon fluctuates day to day, so short results are not the final word. Health Canada recommends a long-term test using an alpha-track detector for at least 91 days in the lowest lived-in level; it is ideal during the heating season, but updated guidance allows testing any time of year. Compare the result against 200 Bq/m³: at or above it, more work is needed; below it, no further action is recommended — though no level is entirely risk-free, so lower is always better.
FAQ
Can I turn my radon fan off at night or in summer? No. Soil gas enters continuously, and the suction under your slab only exists while the fan runs. Turning it off lets radon climb back within hours. Radon fans are designed for 24/7 operation.
Does the manometer show my radon level? No. The U-tube manometer shows the pressure the fan is creating — proof the fan is running. It does not measure radon. Only a radon test tells you your level against the 200 Bq/m³ guideline.
How much does a radon fan cost to run? It is a small, continuous load, closer to a lightbulb left on than a major appliance. The draw depends on the model; it is on the unit's rating plate. The exact monthly cost depends on the fan model and your local electricity rate.
How long does a radon fan last, and how do I know it's failing? Service life and warranty vary by model — check the warranty on the unit your installer fits. Signs of trouble include new grinding or rattling, a louder hum, or a manometer that has gone level.
Do I need to retest after installing or replacing the fan? Yes. A long-term test of at least 91 days is the only way to confirm your home is below 200 Bq/m³. A healthy manometer reading is not a substitute for a radon measurement.
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Sources
- Health Canada — Radon: Reduction Guide for Canadians: https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/radiation/radon-reduction-guide-canadians-health-canada.html
- Health Canada — Radon (main page): https://www.canada.ca/en/health-canada/services/environmental-workplace-health/radiation/radon.html
- Canadian National Radon Proficiency Program (C-NRPP) — Steps to Reduce Radon: https://c-nrpp.ca/steps-to-reduce-radon/
- C-NRPP — Find a Professional: https://c-nrpp.ca/find-a-professional/
- CAN/CGSB-149.12 — Radon mitigation options for existing low-rise residential buildings (referenced in the Health Canada guidance above).
See the numbers for yourself — test, then confirm
Whether you are planning a mitigation system or checking that your fan is still doing its job, it all comes back to measurement. The RadonTest.ca radon test kit is all-inclusive: a C-NRPP-listed detector, tracked shipping both ways, analysis by a Canadian C-NRPP-certified laboratory, and an official Certificate of Analysis reported against Health Canada's 200 Bq/m³ guideline. A long-term test is how you prove the fan — the heart of your system — is keeping your home below the line.
RadonTest.ca does not diagnose, treat, or prevent disease, and is not affiliated with Health Canada or C-NRPP.