Radon myths: is radon only in basements, does granite cause it, can an air purifier or open window remove it, each checked against Canadian evidence.
Photo: Chris Feser from Seattle, USA, CC BY 2.0, cropped, via Wikimedia Commons.
A home’s radon level comes from a measurement and from nothing else. The postal code, the house’s age, a neighbour’s result, an inspection or the countertop do not give it. Every belief below is checked against that, and the verdicts differ. Health Canada’s guidance is a long-term test in the heating season, on the lowest level you live in.
Each belief below carries one of four verdicts, Supported, Partly supported, Not supported or Unproven, with its evidence and the date checked. See how to run a test that counts.
These two beliefs tie radon to a floor or a kind of home. The evidence is a survey average by floor.
89.9, 68.8, 54.4
Bq/m³Geometric mean radon levels below ground, at ground level and above ground, by the floor where the test was placed, in the 2024 Cross-Canada Radon Survey: 23.5% higher below ground than at ground level, and 20.9% higher at ground level than above. A population average, not a rule for any one home.
The claim
“Radon is only a basement problem.”
Our verdict
The claim
“My condo is safe because it is a condo.”
Our verdict
Read how radon gets in and which homes have more.
These three beliefs use a province or another house to stand in for a test of your own. The evidence is the same guidance: another home’s result does not give your level.
The claim
“Radon is only a problem in certain provinces.”
Our verdict
The claim
“Some houses have radon and some do not.”
Our verdict
The claim
“My neighbour tested low, so I am fine.”
Our verdict
See how common high levels are by province and place.
These three beliefs are about where radon comes from and how Canada compares. Each verdict says what the evidence shows.
The claim
“Granite countertops are a major radon source.”
Our verdict
The claim
“Rain pushes radon up, or washes it down.”
Our verdict
The evidence
The claim
“Canada has the highest radon levels in the world.”
Our verdict
The evidence
Read about the geology behind Canada’s levels.
These four beliefs treat a device or a repair as a fix on its own. The evidence sits in the guidance on what lowers a radon level, cited by each verdict.
The claim
“An air purifier, a dehumidifier or a few houseplants will handle it.”
Our verdict
The claim
“Sealing the cracks solves it.”
Our verdict
The claim
“A big exhaust fan in the basement will clear it.”
Our verdict
The evidence
The claim
“An HRV will solve any radon problem.”
Our verdict
Read the questions people ask about ventilation and purifiers.
Both beliefs rest on fresh air, one as a fix and one during the test. The evidence is the measurement guidance, and each verdict says what it means for a window.
The claim
“Opening the windows fixes it.”
Our verdict
The evidence
The claim
“I should open the windows during the test.”
Our verdict
Read the questions people ask about a result.
These three beliefs are about who is at risk and how you would know. Each verdict cites the health evidence and the date we checked it.
The claim
“Radon only matters if you smoke.”
Our verdict
The claim
“You can smell radon, or you would feel symptoms.”
Our verdict
The claim
“Below 200 Bq/m³ there is no risk at all.”
Our verdict
Read how much radon raises lung cancer risk.
These seven beliefs stand in for a long-term test of your home: a short or one-season reading, a monitor spike, any kit or monitor, an old result or an inspection. The evidence is the guidance on a long heating-season test.
The claim
“A quick test is good enough.”
Our verdict
The claim
“Radon levels are about the same all year.”
Our verdict
The claim
“My monitor went over 200, so I have a high radon home.”
Our verdict
The claim
“Any radon monitor sold online works.”
Our verdict
The evidence
The claim
“Any do-it-yourself kit will do.”
Our verdict
The claim
“One low test and I never have to think about it again.”
Our verdict
The evidence
The claim
“The home inspector would have caught it.”
Our verdict
Check whether your home needs a new test.
These seven beliefs are about the fix: how big a job it is, what it costs to run, who needs one and how long it lasts. The evidence starts with Health Canada’s record on how well mitigation works.
More than 80%
Reduction a radon mitigation system brings in most homes, according to Health Canada's Reducing radon levels page (October 2025); a system can be installed in less than a day. Health Canada's September 2026 factsheet, Reduce radon in your home, puts the typical reduction at more than 90%. The two live pages differ, and neither is blended with the national standard's figure for a properly designed active soil depressurization system.
The claim
“Fixing radon means tearing the house apart.”
Our verdict
The claim
“The fan will cost a fortune to run.”
Our verdict
The evidence
The claim
“My builder installed a passive system, so the house is fine.”
Our verdict
The claim
“New homes do not have radon.”
Our verdict
The claim
“Once it is mitigated, it is handled forever.”
Our verdict
The claim
“I have two years to fix it.”
Our verdict
The claim
“A mitigation system hurts resale value.”
Our verdict