A note before you read. This is general consumer information for Canadian apartment and condo residents — renters, owners, and condo/strata boards — drawn from publicly available Health Canada, Take Action on Radon, and U.S. Environmental Protection Agency sources. It is not medical, legal, or warranty advice. Radon results are reported against the Health Canada guideline of 200 Bq/m³; RadonTest.ca coordinates testing logistics and does not interpret individual results or provide health assessments.
Key facts at a glance
- Radon comes from the soil, so it is usually highest in ground-contact and lower levels of a building and tends to decrease the higher you go. That is a tendency, not a guarantee.
- Upper floors are not automatically radon-free. Take Action on Radon puts it plainly: it is "less of a risk the higher up in a building that you live," but "the only way to know the radon level in your living space is to test." No unit is "risk-free" on assumption.
- Health Canada's measurement guidance applies to multi-unit residential buildings — condos and apartments — the same way it applies to houses. Radon doesn't skip a building because it has more than one unit.
- Lower and ground-contact units are the most likely to be elevated — ground-floor suites, garden and basement suites, and any unit with its own contact with the soil. But test regardless of which floor you're on.
- The only way to know YOUR unit is to test it. A neighbour's result, the building's age, or the floor number can't tell you your number.
- Renters can test their own unit. The occupant runs the test; but to fix an elevated level you will usually need the building owner's or the condo/strata board's permission, since the work involves the building structure.
- Use a long-term test of at least 91 days, placed in the lowest lived-in level of your unit, ideally over the heating season.
Does radon affect apartments and condos?
Yes. Radon is a radioactive gas produced by the natural breakdown of uranium in soil and rock, and it enters buildings from the ground — through cracks in the foundation, construction joints, gaps around pipes, floor drains, and sumps. A building having multiple units doesn't change that. Health Canada's measurement guidance covers residential dwellings of all types, including condos, apartments, and multi-unit residential buildings (MURBs), and the same 200 Bq/m³ guideline applies.
The key thing to hold onto is where radon comes from. Because it rises out of the soil, the parts of a building in direct contact with the ground — and the units closest to that contact — are the most likely to see elevated levels. A ground-floor condo sitting on a slab has a far more direct path to soil gas than a unit several storeys up. That's the physical logic behind every "lower units are higher risk" statement you'll read, including Health Canada's own emphasis on testing the lowest lived-in level.
But "most likely" is not "only." Air — and the radon carried in it — moves through a building, so a low reading isn't guaranteed just because a unit is off the ground. The point of this article is to give you a calibrated sense of how floor height changes the odds, and why the only number that actually applies to your home is the one you measure.
Do upper floors have radon?
Generally, the higher you live, the lower the radon risk — but it does not drop to zero, and you should not assume an upper-floor unit is in the clear.
Here's the careful version. Take Action on Radon (the Health-Canada-funded national awareness program led by CARST, CAREX Canada, and the Canadian Cancer Society) states that "primary importance goes to those who are living in dwellings with ground contact, and it is less of a risk the higher up in a building that you live, however the only way to know the radon level in your living space is to test." In the same guidance it notes that, while levels are typically highest in the lowest levels, "air (and radon gas) can move easily throughout the entire space of a dwelling and therefore elevated radon levels can be found in 1st and 2nd floors." So the trend is real and reassuring as far as it goes — but it is a trend, not a guarantee, and elevated readings on lower-but-not-ground floors do happen.
How does radon reach floors above the ground at all? It is generally recognized that radon and other soil gases can migrate upward through a building's vertical pathways — stairwells, elevator shafts, and service chases (the vertical runs that carry plumbing, wiring, and ductwork between floors) — carried by the "stack effect," the natural tendency of warm indoor air to rise and pull air upward through a building, especially in winter. This is a well-established mechanism rather than a precise, quantified rule, so treat it as a reason not to assume an upper unit is radon-free — not as grounds to predict a specific level on a specific floor.
It's worth noting what a body outside Canada recommends, as a useful reference point: the U.S. Environmental Protection Agency recommends testing all units on or below the third floor of a building. That is a U.S. recommendation, not Health Canada guidance — Health Canada frames its advice around testing the lowest lived-in level rather than naming a floor cutoff — but it captures the same idea, that lower floors carry the greater potential and deserve testing.
The bottom line is the one every credible source lands on: the only way to know whether YOUR unit has elevated radon is to test it. Floor number shifts the odds; it never settles the question. Don't assume any unit is "risk-free" — including your own.
Which units are most at risk
If you're trying to gauge where your unit sits on the spectrum, the pattern is driven by proximity to the soil. The units most likely to read elevated:
- Ground-floor and lower units, which sit closest to the soil radon comes from.
- Units with their own in-suite ground contact — for example, a townhouse-style condo or a stacked unit whose floor is a slab directly on the ground.
- Basement suites, garden suites, and below-grade units, which are partly or fully surrounded by soil and tend to see the highest readings in any building, just as a basement does in a house.
- First and second floors, which are generally lower-risk than the ground floor but, as Take Action on Radon notes, can still come back elevated because air and radon move through the building.
That ranking is genuinely useful for setting expectations — but it does not exempt anyone. Higher floors are lower-probability, not no-probability, and the only way to convert a probability into a fact is a test. So the practical rule is simple: if your unit is ground-contact or low, you have extra reason to test promptly; if it's higher up, you still test — you just may be more likely to get a low result. Test regardless of floor.
Renting or in a condo: how to test and what you can do
This is where apartments and condos differ from a single owned house, and it's worth being clear about who does what.
Anyone can test the air in the unit they live in. A radon test detector simply sits in your living space for the test period — you don't need anyone's permission to place a small device in your own home and find out your number. So whether you rent or own your unit, you can run a long-term test yourself and learn where you stand. Take Action on Radon's guidance is explicit that "all Canadians should test their residential space," and that for a rented dwelling "it is best for the occupant to be involved in the testing of the living space."
Fixing an elevated level is a different matter, because mitigation touches the building. Reducing radon usually involves work on the foundation or the building's structure and ventilation — not something a tenant or an individual unit owner can simply do alone. As Take Action on Radon puts it, to make changes to reduce radon levels "you most likely will need permission from the building owner," and in a condo or strata, "you may need permission from the ownership group." A sensible move is to open that conversation when you start testing, so that if your result comes back at or above the guideline, the path to a fix is already in motion rather than starting from scratch.
For the specifics of each situation — your rights and the practical script for raising it — see our guides for renters and for landlords and building owners. If your unit has a below-grade level, our guide to radon in basements covers why those spaces tend to read highest.
How to test your unit
Testing a condo or apartment unit follows the same Health Canada approach as testing a house:
- Use a long-term test — at least 91 days (three months) — ideally run over the heating season, when the unit is closed up and readings best reflect your real annual exposure. Short-term tests vary too much day to day to base a decision on; they're really only appropriate for screening or for checking a system after it's been installed.
- Place the detector in the lowest lived-in level of your unit — the level where you actually spend time (a bedroom, living room, or home office where someone is present at least four hours a day). In a single-level apartment, that's simply the main living area; in a multi-level or basement unit, it's the lowest level you regularly use.
- Follow the placement rules — keep the detector away from windows, exterior doors, vents, and direct drafts, at roughly breathing height, undisturbed for the full test period. Our guide on where to place your radon test kit walks through the distances and the do's and don'ts.
- Read your result against the guideline. When the lab report comes back, you'll compare your annual-average number to Health Canada's 200 Bq/m³ guideline. Our walkthrough on how to read your radon test results explains what the number means and what to do next.
If your long-term result is at or above 200 Bq/m³, Health Canada recommends taking action to reduce it within one year — and sooner the higher the level. In a condo or apartment, "taking action" means starting the conversation with your building owner or condo/strata board about a fix, since the work involves the building. (A five-year retest interval applies specifically to homes that have already been mitigated, to confirm the system is still working.)
When you're ready, you can order a long-term kit here.
Frequently asked questions
Can an apartment have radon? Yes. Radon comes from the soil and enters buildings from the ground, and Health Canada's measurement guidance applies to apartments and multi-unit residential buildings just as it does to houses. Levels are usually highest in ground-contact and lower units, but any unit can have radon — the only way to know yours is to test.
Do high-rise or upper-floor units have radon? Generally, the higher up you live, the lower the risk — but it isn't zero. Take Action on Radon describes upper floors as "less of a risk," while stressing that "the only way to know the radon level in your living space is to test." Radon and air can move upward through a building's stairwells, elevator shafts, and service chases, so an upper-floor unit is lower-probability, not guaranteed radon-free.
I'm on the 10th floor — am I risk-free? Lower risk, but not zero — so test rather than assume. A high floor meaningfully reduces the odds of an elevated reading, but no credible source will call any unit "risk-free" without a measurement. A long-term test in your unit is the only way to confirm your actual level.
Can I test a rented apartment? Yes. You don't need anyone's permission to place a radon test detector in the home you live in and find out your number — Take Action on Radon recommends that the occupant be involved in testing their own living space. What does require permission is fixing an elevated level, since mitigation involves the building. See our renters' guide.
Who fixes radon in a condo? Because mitigation involves the building's foundation, structure, or ventilation, it generally isn't something an individual unit owner or tenant arranges alone. You'll usually need the building owner's or the condo/strata board's agreement, and the work should be done by a C-NRPP-certified mitigation professional. Starting that conversation when you begin testing makes the path smoother. Our landlords' and building-owners' guide covers the responsibilities involved.
Is radon worse in basement suites? Basement and garden suites tend to read among the highest in any building, because they're partly or fully surrounded by the soil radon comes from — the same reason basements read highest in houses. If you live in a below-grade unit, you have extra reason to test promptly. Our guide to radon in basements explains why.
Does my floor number tell me whether I need to test? No. Floor height shifts the odds — lower units are more likely to be elevated, higher units less likely — but it never settles the question for your specific unit. Everyone should test their own living space regardless of floor; the only number relevant to your health is the one you measure.
My building is new — is it already protected? Not necessarily. Newer buildings may include radon-control rough-ins under building codes, but a rough-in is a passive measure, not a guarantee, and it doesn't replace testing. Test your unit like any other, and compare your result to the 200 Bq/m³ guideline.
Find out your unit's number
Floor height changes the odds, but it never answers the question for your specific home — and no unit should be assumed "risk-free" without a measurement. Whether you rent or own, on the ground floor or the tenth, the only way to know your unit's radon level is a long-term test of at least 91 days.
Order your RadonTest.ca kit → — lab analysis by a C-NRPP-certified laboratory (with an all-in-Canada analysis option), tracked shipping both ways, and your result delivered with clear Health Canada context.
Sources
- Health Canada — Guide for radon measurements in residential dwellings (homes) (measurement guidance applies to residential dwellings including condos, apartments, and multi-unit residential buildings; long-term testing of at least three months in the lowest lived-in level; placement). https://radontest.ca/links/hc-measurements-guide
- Take Action on Radon — Frequently Asked Questions (rented/condo dwellings: "less of a risk the higher up in a building that you live," "the only way to know the radon level in your living space is to test," occupant involvement and owner/strata permission to make changes; "elevated radon levels can be found in 1st and 2nd floors"; levels typically highest in the lowest levels), modified 2024-06-14. https://takeactiononradon.ca/learn/frequently-asked-questions/
- Health Canada — Radon: What you need to know (radon enters from the soil through foundation openings; 200 Bq/m³ guideline; corrective action within one year, sooner the higher), 2025 edition. https://radontest.ca/links/hc-what-you-need-to-know
- U.S. Environmental Protection Agency — A Citizen's Guide to Radon (U.S. recommendation to test all homes/units on or below the third floor; radon highest in lowest levels). https://www.epa.gov/radon/citizens-guide-radon-guide-protecting-yourself-and-your-family-radon
The upward-migration mechanism (radon moving through stairwells, elevator shafts, and service chases via the stack effect) is a generally recognized phenomenon and is not attributed to a specific Health Canada figure. The "test on or below the third floor" recommendation is from the U.S. EPA, not Health Canada. Lab analysis is performed independently by a C-NRPP-certified laboratory; results are reported against the Health Canada guideline of 200 Bq/m³. RadonTest.ca coordinates kit logistics and sample submission only — it does not interpret or modify lab results and does not provide medical, legal, or warranty advice. Information attributed to Health Canada, Take Action on Radon, and the U.S. EPA is summarized from the public sources listed above; confirm time-sensitive details with the responsible body.