Read this first. This article provides general information for Quebec homeowners, buyers, sellers, landlords, and tenants, drawn from public sources published by Health Canada and the Canadian National Radon Proficiency Program (C-NRPP). It is not medical, legal, or warranty advice. Radon results are presented relative to Health Canada's guideline of 200 Bq/m³; RadonTest.ca coordinates the logistics of testing and does not interpret individual results or provide any health assessment. The decision to fix a home should rest on a completed long-term test and, when the level is elevated, on the advice of a C-NRPP-certified mitigation professional.
It's one of the most common questions among Quebec homeowners: "I already have an air exchanger — doesn't it take care of the radon?" The honest answer fits in one sentence, then deserves a few nuances. An air exchanger — in Quebec, almost always a heat recovery ventilator (HRV) — dilutes radon by bringing in fresh air from outside; according to Health Canada, this could reduce it by roughly 25 to 50% in most homes. That's real, but partial and conditional: it is not a substitute for fixing the problem at the source (active soil depressurization), it has to be balanced so it doesn't make things worse, and you have to retest to confirm. Here's what Health Canada says, figure by figure.
See the Canada radon map — measured results for every surveyed area, searchable by postal code.
The essentials at a glance
- An HRV dilutes radon; it does not remove it at the source. It could lower concentrations by roughly 25 to 50% in most homes (Radon — A Guide for Canadian Homeowners on Reduction, Health Canada, modified September 2025).
- The effectiveness of ventilation is limited and "appropriate only when modest reductions are needed"; it works best in tightly sealed homes with very low natural air exchange (Health Canada, 2025).
- Balancing is mandatory. An unbalanced HRV can depressurize the home and draw in more radon — the opposite of the intended effect (Health Canada, 2025).
- For a large reduction, ventilation isn't the answer. For a drop of 50% or more, Health Canada recommends active soil depressurization (Health Canada, 2025), which reduces radon by more than 80% in most homes (Health Canada, Reducing Radon Levels in Your Home, modified October 2025).
- The action level is 200 Bq/m³ as an annual average; there is no risk-free level, and a result at or above it calls for action within the year — sooner if the level is high (Health Canada).
- Test first, then reconfirm. If you're relying on an HRV, a new long-term test is the only way to know whether it actually brought you below 200 Bq/m³.
What an air exchanger (HRV) is, and why Quebec is full of them
If you live in Quebec, chances are you have an air exchanger — the everyday name for a heat recovery ventilator (HRV). It's a piece of ventilation equipment designed for cold climates that has become a standard of Quebec residential construction, because our homes are closed up and heated for much of the year. A modern, tightly sealed home lets in very little fresh air on its own; an HRV solves this by exhausting stale air and replacing it with fresh air from outside, while recovering the heat along the way through a heat-exchange core. As Health Canada describes it, "an HRV increases ventilation by drawing in air from outside while using the heated or cooled air being exhausted to warm or cool the incoming air" (Health Canada, 2025). It thereby manages humidity, window condensation, and air quality. (A close cousin, the energy recovery ventilator (ERV), also transfers some of the moisture; for radon, Health Canada treats the HRV and the ERV the same way.) The question that matters here: to what extent does this air exchange also act on radon?
What Health Canada says precisely about HRVs and radon
This is where you have to be exact, because it's the part homeowners often misread.
An HRV dilutes radon — by roughly 25 to 50%. According to Health Canada, "an HRV could lower radon concentrations by 25 to 50 percent in most homes" (Health Canada, 2025). More fresh air coming in means more dilution — but note the ceiling: at best, an HRV removes about half.
The effectiveness of ventilation is limited — and reserved for modest reductions. Health Canada states it plainly: "The effectiveness of ventilation at reducing radon is limited and appropriate only when modest reductions are needed" (Health Canada, 2025). It's a tool for nudging a result that's already close to the guideline — not for bringing a high result below the threshold. It also works best "in homes that are more tightly sealed and have very low natural air exchange rates."
The crucial point: balancing. Health Canada writes that "it is important to ensure that this type of system has balanced incoming and outgoing air flows so that the home is not depressurized, which can draw in more radon" (Health Canada, 2025). It's counterintuitive: radon enters largely because the indoor air is usually at a slightly lower pressure than the soil, which pulls the gas in through cracks. An unbalanced HRV — one that exhausts more air than it brings in — deepens this negative pressure and can therefore increase radon entry. Used against radon, an HRV must run continuously, stay balanced, and have its filters maintained.
And when you need a real reduction? Health Canada is explicit: "When a substantial reduction in radon concentrations (of 50 percent or more) is wanted, active soil depressurization is the approach that is recommended most of the time" (Health Canada, 2025). Modest reduction → ventilation can play a role; large reduction → active soil depressurization.
In short, an HRV does not "fix" or "eliminate" radon: it's a partial, conditional measure. To place it among the mitigation methods, see how radon mitigation works in Canada.
When an HRV can help — and when you need active soil depressurization
The difference between "an HRV might be enough" and "you need to fix the source" depends mostly on how far your result is above the guideline.
When an HRV can play a supporting role. A modest exceedance — say around 230 or 250 Bq/m³ — in a tightly sealed, well-built home, as many recent Quebec homes are. For a reduction of that order, the 25-to-50% range of a well-balanced HRV can, in theory, be enough to get below 200. Two caveats: many homeowners still go straight to ASD, which is more reliable; and you have to retest to confirm.
When an HRV isn't enough. As soon as your result is well above the threshold — 400, 700, 1,000 Bq/m³ or more — ventilation is no longer the right answer: cutting a result of 800 by 25 to 50% still leaves you far above 200. This is the case Health Canada is addressing when it recommends active soil depressurization (ASD). This method tackles radon at the source: a pipe running through the slab, fitted with a continuously running fan, draws the gases from the soil and vents them outside, while reversing the pressure difference that pulls radon into the home. According to Health Canada, it "will lower radon concentrations by more than 80%" in most homes, "can be installed in as little as one day," and costs "about the same as other common home repairs" (Health Canada, Reducing Radon Levels in Your Home, modified October 2025).
The fundamental distinction: an HRV dilutes a problem; ASD removes it at the source. Note too that radon concentrates at the lowest level of the home — an HRV acts on the ambient air, but not on that entry pathway beneath the slab (see radon in basements in Canada). If your result calls for a fix, start with what to do if your radon level is above 200 Bq/m³, then see how to choose a radon mitigator and how much radon mitigation costs in Canada.
A caution specific to cold climates: backdrafting
One point Health Canada expressly raises, and that matters in Quebec, where we heat with wood, oil, or gas: any intervention that changes the balance of air pressures — an unbalanced HRV as much as a poorly designed mitigation system — can, in the worst case, cause backdrafting, that is, pull the combustion gases from a furnace, water heater, fireplace, or wood stove back into the home. In its tables of mitigation options, Health Canada in fact flags the measures that alter pressures with a warning about the "possibility of backdrafting from combustion appliances" (Health Canada, 2025). Balancing an HRV is therefore not a comfort detail but a safety matter — and one more reason to leave the adjustment and the verification to a qualified person.
The practical bottom line: test first, reconfirm afterward
1. Test first. You can't know whether your HRV is "enough" without knowing your starting level. Health Canada recommends a long-term test of at least 91 days (about three months), ideally during the heating season, in the lowest lived-in level; a short-duration snapshot won't do. For the details of the current guidance — including the fact that you can test in any season — see Health Canada's radon testing guidance.
2. Interpret the result. Below 200 Bq/m³, no fix is required (though no level is entirely risk-free). At or above 200, you need to act — and the size of the exceedance tells you whether an HRV might play a supporting role (modest exceedance, tightly sealed home) or whether you need ASD from the start.
3. If you're relying on an HRV, reconfirm with a new test. This is the step people skip, and the most important. An HRV's effectiveness depends on how tightly the home is sealed, on its balancing, and on its maintenance: the only proof that it actually brought you below 200 Bq/m³ is a new long-term test, ideally over a heating season. On timing, see how often to retest radon in Canada.
Frequently asked questions
Does an air exchanger reduce radon? Yes, but partially. An HRV dilutes radon by bringing in fresh air; according to Health Canada, it could lower it by roughly 25 to 50% in most homes (Health Canada, 2025). It does not remove it at the source. For a larger reduction, Health Canada recommends active soil depressurization.
Is an HRV enough to fix a radon problem? It depends on your level. Health Canada notes that the effectiveness of ventilation is limited and appropriate only for modest reductions (Health Canada, 2025). If your result is modestly above 200 Bq/m³ in a tightly sealed home, a well-balanced HRV can help — provided you retest to confirm it. If it's well above, an HRV won't be enough and active soil depressurization is the recommended solution.
HRV or ERV — which is better for radon? For radon, Health Canada treats the HRV and the ERV the same way: both dilute radon by roughly 25 to 50% in most homes, under the same conditions (Health Canada, 2025). Their difference comes down to moisture transfer (the ERV transfers some of it), which is a matter of comfort, not radon performance. In both cases, balancing the air flows is essential.
Can an unbalanced air exchanger increase radon? Yes. Health Canada warns that a system must have balanced flows "so that the home is not depressurized, which can draw in more radon" (Health Canada, 2025). An HRV that exhausts more air than it brings in can deepen the negative pressure and increase radon entry.
By how much does active soil depressurization reduce radon, compared with an HRV? Much more. An HRV removes about 25 to 50% at best; active soil depressurization reduces radon by more than 80% in most homes, and it's the recommended method for a drop of 50% or more (Health Canada, 2025). ASD works at the source; the HRV dilutes gas that has already entered.
I already have an air exchanger. Should I still test my home? Absolutely. An HRV doesn't tell you your radon level and doesn't prove you're below 200 Bq/m³. The only way to know is a long-term test of at least 91 days — which is also the only way to confirm the HRV is actually doing the job.
Test first — then decide with full knowledge
An air exchanger makes your home more comfortable and can contribute modestly to reducing radon under the right conditions. But it does not replace the one step that truly matters: knowing your number. Test first; you'll then know whether an HRV can help or whether you need active soil depressurization — and, in every case, a new test will confirm that the radon is under control.
Order your RadonTest.ca kit → — analysis by a C-NRPP-certified laboratory (with an option for analysis entirely within Canada), tracked round-trip shipping, and your result delivered with clear Health Canada context.
Sources
- Health Canada — Radon: A Guide for Canadian Homeowners on Reduction (HRV/ERV: dilutes radon by 25 to 50% in most homes; effectiveness of ventilation limited and appropriate only for modest reductions; ventilation most effective in tightly sealed homes with low air exchange; balanced incoming/outgoing flows mandatory, otherwise depressurization that draws in more radon; active soil depressurization recommended for a drop of 50% or more; backdrafting warnings for combustion appliances), published February 2023, modified 2025-09-24. https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/radiation/radon-reduction-guide-canadians-health-canada.html
- Health Canada — Reducing Radon Levels in Your Home (active sub-slab depressurization = the most common method; reduction of more than 80% in most homes; installation in one day; guideline of 200 Bq/m³; hiring a C-NRPP-certified professional), modified 2025-10-09. https://www.canada.ca/en/health-canada/services/health-risks-safety/radiation/radon/reducing-levels-home.html
- Health Canada — Guide for Radon Measurements in Residential Dwellings (long-term test of at least 91 days; heating season; lowest lived-in level; what to do based on the result; retesting), modified 2025. https://www.canada.ca/en/health-canada/services/publications/health-risks-safety/guide-radon-measurements-residential-dwellings.html
- C-NRPP — Find a Professional (directory of professionals and laboratories certified in radon measurement and mitigation). https://c-nrpp.ca/find-a-professional/
Laboratory analysis is performed independently by a C-NRPP-certified laboratory; results are presented relative to Health Canada's guideline of 200 Bq/m³. RadonTest.ca coordinates only the logistics of the kits and sample submission — it does not interpret or alter laboratory results and does not provide medical, legal, or warranty advice. C-NRPP certifies laboratories, detectors, and professionals, not companies. Information attributed to Health Canada and C-NRPP is summarized from the public sources listed above; confirm details subject to change with the responsible body. There is no risk-free level of radon; a result below 200 Bq/m³ means no action is recommended, not that the risk is zero.