Radon is tasteless, colourless and odourless.
This invisible gas seeps silently from the ground into buildings, accumulating in basements and living spaces where it can pose a significant threat to human health.
“Humans tend to turn down the volume on what they can’t feel, see, smell, hear,” said Aaron Goodarzi, a researcher at the University of Calgary who directed a national study aimed at preventing radon exposure and lung cancer.
While the risk of exposure is relatively low in open air, problems arise when buildings trap it indoors.
“Buildings don’t actually concentrate radon,” said Goodarzi. “They prevent it from being diluted.”
This makes radon testing essential, experts say.
“ It’s all about testing every home, because there’s radon everywhere,” said Julie Girardeau, operations manager at Airthings, which manufactures digital radon detectors and other air quality monitoring devices.
“ You could have two homes side-by-side on the same plot and have very different radon levels.”
The invisible threat
Radon forms naturally as the uranium in soil and rock breaks down, releasing radioactive gas that moves up toward the surface.
“Radon is always being generated deep underground and migrating to the surface through soil gas,” said Goodarzi.
Outdoors, that gas quickly disperses to levels that are generally harmless. Indoors, the situation can be very different.
“The built environment is the primary means by which we are exposed to radon,” said Goodarzi.
When radon enters buildings through foundations, pipes or small openings in floors and walls, it can accumulate in enclosed spaces, where it presents a serious risk to humans.
When inhaled, the gas releases radiation in the alveoli — the tiny air sacs in the lungs where oxygen enters the bloodstream. That radiation can damage the lung cells and accelerate cellular aging, increasing the risk of developing cancer over time.
Radon is the leading cause of lung cancer among non-smokers, and lung cancer is the leading cause of cancer deaths in Canada, claiming about 19,000 lives each year.
Why long-term monitoring matters
Many Canadians only encounter radon testing when completing a real estate transaction. However, these one-off tests provide a limited snapshot of the risks.
“Radon literally can change with the weather,” said Goodarzi.
Changes in atmospheric pressure can affect how much gas enters a building. Seasonal changes — such as opening windows in summer — can also dramatically influence indoor radon levels.
One-time tests can therefore fail to present a complete picture of the risks.
“The risk of false positives and false negatives for a health decision is profound,” Goodarzi said.
Homeowners also rely too heavily on regional radon maps when assessing their risk, says Girardeau, of Airthings.
While some areas of Canada — including parts of the Prairies, Western Quebec and Atlantic Canada — are known to have elevated radon levels, exposure risk can actually vary within neighbourhoods and even between levels in a house, Girardeau says.
“ In Canada especially, where a majority of our houses are heated with forced-air ventilation, the difference of radon between floors is simply about 20, 25 per cent tops,” said Goodarzi. “And so radon is not just a problem of the basement; it is a problem of every floor in a house.”
Because radon levels fluctuate over time, experts generally recommend testing for at least 90 days in the part of the home where people spend the most time.
Disposable, self-administered testing kits, including the charcoal canister variety, are widely available. However, as Girardeau points out, short-term testing approaches “only offer a snapshot” of a metric in flux.
“ So many other variables like weather patterns and ventilation changes might influence the test,” she said.
Single-use, long-term radon test kits are both appropriate and reliable. When deployed for a minimum of three months, ideally during the colder months, they account for these variations and provide an accurate representation of average radon exposure.
“ That’s why long-term, yearly monitoring is the way to go,” said Girardeau. “You know what’s happening. You have a true picture of your radon levels.”
To improve access to testing, Airthings has also supported radon detector lending programs through libraries and other public facilities across Canada.
The initiative, developed in partnership with organizations such as the BC Lung Foundation, allows residents to borrow monitors for several weeks and assess their exposure at home.
The goal is to make testing more accessible, says Girardeau, particularly for people who may not be able to purchase a device.
“Too many people were not testing because some couldn’t afford it,” said Girardeau, who has been heavily involved in the initiative.
Airthings’ Canadian Library Program, which was inspired by a similar initiative in Norway, has been active for about 10 years.
“It was all about bringing equity back — and making testing not a question of affordability, but making it available to anybody who wants to test,” said Girardeau.
Airthings also maintains an online map that provides aggregate radon-level data for homes in a given area, which can be a useful tool for gauging regional risk.
Protecting the home
While radon remains the most serious radiation-related air risk in homes, it is only one element of indoor air quality. Increasingly, Canadians are also dealing with other airborne concerns, from wildfire smoke to poor ventilation.
Airthings has developed air monitoring systems that track radon alongside other indicators such as carbon dioxide, particulate matter, volatile organic compounds (VOCs), humidity and temperature.
In Canada, consumer radon monitors can be verified through the Canadian National Radon Proficiency Program, which maintains a list of approved devices that meet reliability standards.
Airthings’ Corentium Home and View Plus monitors are among those approved by the program.
These systems can help homeowners understand how everyday activities affect the air inside their homes.
A crowded gathering in a basement can raise carbon dioxide levels. Cleaning products or fresh paint can increase VOC concentrations. Particulate matter can spike dramatically during wildfire seasons.
Monitoring these changes allows homeowners to make practical adjustments, such as opening windows, improving ventilation or adjusting how indoor spaces are used.
“ It helps us make informed decisions on our ventilation, the occupancy, how we use our space, instead of just guesswork,” said Girardeau, noting that Airthings’ monitoring app allows for real-time updates on a user’s mobile device.
Air quality also interacts with radon risk. Airborne particulates — whether from tobacco smoke, vaping, air pollution or wildfire smoke — can act as carriers for radioactive radon decay products, says Goodarzi.
“Dirty air increases the dose that you get from radon,” he said.
Air filters can reduce particulate pollution, but they cannot remove radon gas itself. That makes detection and mitigation the most effective ways to manage exposure.
Fortunately, if radon is detected, the engineering solution is often straightforward. Radon mitigation systems can vent soil gases safely outside the home and permanently reduce indoor concentrations.
“Radon can be mitigated in any house with one day’s work, essentially,” said Goodarzi.
For homeowners, the takeaway is simple: radon may be invisible, but it is not unknowable. With modern monitoring technology, Canadians can easily measure the air they breathe — and take steps to ensure they stay safe.
To learn more about Airthings and its air monitoring devices, visit www.airthings.com/en-ca/
