Reducing radon
How do you reduce radon?
The standard solution is sub-slab depressurization: a fan draws radon from the soil before it enters the house and vents it outside. Health Canada recommends taking action when the concentration exceeds 200 Bq/m³. Hire a certified professional for the installation, then re-measure to confirm the result.
When to act
Act above 200 Bq/m³. That is the Canadian guideline, the one the map already displays: Health Canada recommends mitigation there. After the work, aim for as low as possible. Between 100 and 200 Bq/m³, it is worth monitoring — re-measure or consider a long-term test, with no urgency. Under 100 Bq/m³, it is acceptable. Whatever your situation, the starting point is a long-term measurement. (Health Canada)
The standard approach: sub-slab depressurization
The reference method is sub-slab depressurization, installed by a professional. Concretely: a pipe runs through the concrete slab, and a fan continuously draws the gas from the soil under the house. The gas is vented outside before it enters the living spaces. Depending on the configuration, complementary techniques are added: crawl-space ventilation, sealing cracks and joints around entry points. Sealing is a useful complement — never a solution on its own. (WHO) (EPA)
Effectiveness
Yes, mitigation works — and measurably. A passive system, without a fan, typically reduces the indoor radon concentration by more than 50%. An active system, with a fan, achieves even greater reductions. That is a typical reduction, not a guarantee: whatever the technique, the result is only established by measuring again (see below). (WHO)
Radon mitigation works, and measurably so. A passive sub-slab depressurization system typically cuts the indoor concentration by more than 50%; an active system — the same pipe, connected to a fan — achieves even greater reductions. The goal is the guideline itself: bring a home above 200 Bq/m³ back under that threshold, and keep it there. The outcome is not declared in a quote. It is established by a long-term re-measurement, 91 days or more, under real occupancy conditions. In both cases the target remains the soil under the house — intercepted before it reaches the air you breathe. That double proof, the certified installation and the measurement that confirms it, is what separates a successful mitigation from work merely paid for. (WHO)
Cost: an indicative range
Expect $500 to $3,000 for partial work or do-it-yourself solutions. (Health Canada) For a complete system installed by a certified C-NRPP/CHNP contractor, expect $2,500 to $5,000. (Take Action on Radon)
The two ranges do not cover the same work. They remain planning ranges, never quotes: every house is different. The best anticipated cost is the one a professional gives after seeing yours.
Are there financial assistance programs?
No, as of the verification date below: none of the official sources followed by this page — (Health Canada), (the C-NRPP), (Take Action on Radon) — listed a permanent financial assistance program dedicated to radon mitigation in Quebec. Home-renovation programs with an energy component appear and disappear over the years, federal and provincial alike, and their eligibility rules change. Before planning work, check the current state with those same organizations. Assistance introduced in the meantime will only be mentioned here once verified and dated. Until then, the two ranges above remain the realistic planning baseline.
Last verified (assistance): 2026-08-28
What does an installation involve?
The rollout comes in three stages. Before: the certified professional starts from your long-term measurement. They inspect the basement or crawl space, identify the best place to pass the pipe through the slab and where the fan will sit, then give a quote — the ranges above serve as the order of magnitude. During: one hole through the slab, the pipe installed, cracks and joints around it sealed, the fan mounted, and a vent line releasing the gas above the roofline, away from openings. After: the system runs continuously and quietly. The confirmation does not come from the quote — it comes from a long-term re-measurement, 91 days or more, under the protocol described above. (C-NRPP)
Certified professionals
In Canada, radon professionals’ proficiency is certified by the C-NRPP — the Canadian National Radon Proficiency Program. Expect that certification: for a system installed to professional standards, use the official directories of certified professionals. (C-NRPP) (Take Action on Radon)
Are you a tenant?
Yes, you can act. Measure first: a dosimeter exposed for 91 days or more requires neither permission nor work — you can find out your home’s concentration yourself. Then inform the landlord in writing, attaching the result: Health Canada’s 200 Bq/m³ guideline applies to every dwelling, rented or owner-occupied. While waiting for an answer, two levers remain within your reach: sealing the visible cracks in the slab and the walls in contact with the soil, and airing the lowest rooms regularly. If the result exceeds 200 Bq/m³, request an intervention by a certified professional in writing — that is the normal route — and keep a copy of your exchanges. (Health Canada)
Can ventilation (HRV) reduce radon?
Yes, but as a complement only. A heat recovery ventilator (HRV) continuously renews indoor air, and that dilution lowers the radon concentration — without eliminating it: fresh air carries radon of its own, and the soil under the house keeps pushing more. Sub-slab depressurization acts at the source; ventilation dilutes the result. An HRV is therefore a useful complement — for instance in a borderline case, between 100 and 200 Bq/m³ — never a substitute for depressurization when the guideline is exceeded. (WHO) (EPA)
Re-measuring after mitigation
Always re-measure: 91 days or more after mitigation, the same protocol as the initial test, under the same seasonal conditions. A mitigation is only confirmed by that new long-term measurement. On the map, post-mitigation measurements appear in the “800 (45)” format: the value before the work, followed in parentheses by the value measured after. The legend’s convention keeps visible both the corrected problem and the proof that it can be corrected.
A new detector is needed for this re-test: where to get a detector.
New construction
The right time to prevent is construction itself. In a new house, a mitigation rough-in can be installed during construction: the pipe through the slab is put in place, ready to be connected to a fan if a measurement later reveals a high concentration. That is far simpler and less expensive than breaking into a finished slab. (C-NRPP)
To understand where radon comes from and how to read a measurement: what radon is. Once your mitigation is done and re-measured, you can add your measurement to the map — anonymously, before and after the work.
Last verified: 2026-08-28