Testing is the only way to know the radon level in your home. You cannot see, smell, or taste radon, and results can differ dramatically between neighbouring houses.
For the clearest estimate of long-term exposure, Health Canada recommends testing for 3 to 12 months, with at least 91 days of the measurement occurring during the heating season. A shorter electronic screening can provide a useful snapshot when information is needed sooner, but it should not be treated as a substitute for a long-term result.
ATMOS offers both short-term electronic screening and long-term testing. We also often recommend that homeowners purchase a reliable C-NRPP-listed consumer monitor so they can continue tracking their home before and after mitigation.
What kind of radon test should you use?
There is no single test that is best for every situation. The right option depends on whether you want a quick preliminary snapshot, an estimate of long-term exposure, or confirmation that a mitigation system is working.
Consumer electronic radon monitor
A reputable consumer electronic radon monitor takes repeated measurements and shows averages over time. It can remain in the home for months or years, allowing the homeowner to see seasonal changes and confirm that a mitigation system continues to perform.
This is often the most useful option for homeowners who want ongoing information. After testing your own home, the monitor can also be used by family members or friends, provided it is reset and placed correctly each time.
Choose a model that has passed C-NRPP performance testing. Product quality and stated accuracy vary, and a low-cost unlisted monitor should not automatically be assumed reliable.
View C-NRPP’s list of tested consumer electronic radon monitors.
Passive long-term test
A passive test, such as an alpha-track detector, does not require power. It remains in the home for the required testing period and is then sent to a laboratory for analysis.
These tests are affordable and straightforward, but placement, start and end dates, and handling instructions still matter. Choose a C-NRPP-approved device from an appropriate laboratory or supplier.
Professional electronic testing
Professional electronic radon monitors are maintained under professional quality-control requirements and can produce detailed time-based data and a written report.
Professional testing may be useful when:
- A homeowner does not want to purchase or manage a device
- A properly documented short-term screening is needed
- A home purchase or sale creates a time-sensitive need for information
- A homeowner wants help selecting the correct location and interpreting the result
- A short-term post-mitigation test is being performed to confirm that a system is responding
ATMOS does not publish one testing package for every home. Contact us and we will help determine which option is appropriate for your situation.
What is the difference between short-term and long-term testing?
Under current C-NRPP terminology, a short-term radon test lasts at least 48 hours but less than 91 days. A long-term test lasts 91 days or more.
Short-term screening
A short-term electronic screening shows the radon concentration during a limited period. It can identify a potentially serious issue and provide useful preliminary information, particularly when performed during colder conditions.
However, radon changes with weather, seasons, ventilation, and occupant behaviour. A short measurement may be much higher or lower than the home’s annual average. Health Canada therefore advises against using a short-term result by itself to determine whether a home exceeds the Canadian guideline or requires mitigation.
Long-term measurement
A long-term measurement smooths out daily and seasonal fluctuations and provides a much better estimate of average exposure. Health Canada recommends a test lasting 3 to 12 months, with a minimum of 91 days during the heating season.
When comparing a result with Canada’s action level of 200 Bq/m³, use the longest representative average available—not a single hourly spike or one unusually low day.
Where should a radon test be placed?
The purpose is to measure the air people normally breathe. Health Canada recommends placing the device on the lowest lived-in level of the home, in a room occupied for an average of at least four hours per day.
Good testing rooms may include:
- A basement bedroom
- A home office
- A family or recreation room
- A playroom
- A main-floor living area when the basement is not regularly occupied
Avoid testing in:
- Mechanical rooms
- Bathrooms, kitchens, and laundry rooms
- Closets or storage rooms
- Crawlspaces
- Areas directly beside an open sump or exposed foundation crack
A reading taken beside a sump may describe a radon entry point rather than the concentration in the air occupants normally breathe.
How should the device be positioned?
Current Health Canada guidance recommends that the device be:
- At least 30 cm above the floor
- At least 30 cm away from walls or ceilings
- At least 1 metre from windows, exterior doors, and air vents
- Away from direct sunlight, heat, humidity, and strong air currents
- Away from electronics or network equipment that could interfere with some devices
- Surrounded by enough open space for normal airflow
- Placed somewhere children and pets will not disturb it
A shelf, table, or dresser in an appropriate occupied room often works well. The device should remain in the same location for the measurement period.
How should you operate the home during testing?
The instructions depend on the type of measurement.
During a short-term professional screening
Short-term testing is intended to measure the home under controlled conditions. Follow the instructions provided for that specific test. This commonly includes:
- Keeping exterior windows and doors closed except for normal entry and exit
- Not operating portable fans or equipment that deliberately brings outdoor air into the home
- Limiting unnecessary or extended use of kitchen and bathroom exhaust fans
- Keeping permanently installed heating, cooling, HRV, and ventilation systems operating in their normal configuration unless the testing professional instructs otherwise
- Leaving the testing device untouched in its original location
During a long-term test
Live normally. Do not change your habits simply to raise or lower the displayed number. Health Canada recommends that residents maintain their normal lifestyle during a long-term measurement so the result reflects typical exposure.
Consistency matters. Moving the device between rooms or changing ventilation habits throughout the test makes the result harder to interpret.
Is winter the best time to test in Calgary?
Winter is an important part of radon testing in Calgary. During the heating season, homes are closed more tightly and the stack effect is stronger. Warm air rising through the building can create lower pressure in the basement, drawing more soil gas through foundation openings.
As a result, indoor radon is often higher during colder months. A winter screening may provide a conservative snapshot, but it still does not automatically equal the home’s annual average.
You can begin a long-term test at any time. Current Health Canada guidance says the measurement should include at least 91 days during the heating season. If a test contains fewer than 91 heating-season days and the result is below 200 Bq/m³, additional testing during the next heating season may be needed because the measurement could underestimate annual exposure.
What happens when ATMOS performs a radon test?
We begin by asking about the home, how the basement is used, and why the homeowner wants to test. We then recommend a suitable testing approach and place the device in an appropriate occupied area.
At the end of an ATMOS testing service, we:
- Collect the testing device when applicable
- Provide the homeowner with the available results or report
- Explain the average measured during the test period
- Put the number in context with the Canadian guideline
- Explain the limitations of a short-term snapshot when applicable
- Recommend continued testing or mitigation where appropriate
If the result indicates elevated radon, we can arrange a separate mitigation estimate and explain how an active system would reduce the level.
Common radon-testing mistakes
The most frequent problems are simple and avoidable:
- Using an unlisted monitor. A product being sold online does not prove that it has passed independent performance testing.
- Testing in the wrong room. Mechanical rooms, storage areas, and locations directly beside sumps or cracks do not represent normal occupied exposure.
- Moving the device. Radon can vary between rooms and floors. Keep the device in one appropriate location for the full measurement.
- Stopping too soon. A few hours or days can be interesting, but they do not establish the annual average.
- Reacting to individual spikes. Use the longest representative average rather than focusing on one high or low reading.
- Changing the home during the test. Unusual window, fan, or ventilation use can make the measurement less representative.
Start with the right test
You do not need to understand every detector or testing protocol before contacting us. Tell us about your home and why you would like to test, and ATMOS will help you choose an appropriate option.
Contact ATMOS and tell us what you want to learn from the test. We’ll recommend an appropriate option and explain the current service details.
Sources
- Health Canada: Guide for Radon Measurements in Homes
- C-NRPP: Consumer-Grade Electronic Radon Monitors
- C-NRPP: Listed Professional Devices