Where should I place my radon detector?

This tool asks two things: the lowest level of your home where someone spends more than four hours a day, and a room on that level. It then gives the spot in that room where the detector goes. It cannot measure the radon in your home; only a test can do that. It makes no claim about your health.

Test the lowest level where someone spends time every day

Test a normal occupancy area on the lowest lived-in level of your home. A normal occupancy area is one where someone spends more than four hours a day. A space used less than daily counts if it averages that over a year, like a basement studio busy on weekends.

The lowest lived-in level is the lowest floor with such an area. A basement counts only if people use it as living space. If it is unfinished and rarely used, the main floor is that level. Test a home above ground level too, including an upper-floor apartment.

• Counts: a finished basement family room, bedroom, office or playroom.
• Counts: a basement workshop or a basement apartment.
• Does not count: crawl spaces, unfinished basements and cold rooms.
• Does not count: storage areas, furnace rooms and laundry rooms.
• Does not count: any area normally closed off or rarely used.

See what a normal occupancy area is and what 200 Bq/m³ means.

Pick a bedroom, family room or office, not the kitchen, bathroom or laundry

Test in a family room, living room, den, playroom, office or bedroom, or in a basement workshop or basement apartment that someone uses more than four hours a day. Bedrooms come first, on the main floor or in the basement. Where children live in the home, a basement playroom comes next. Do not test in the kitchen, laundry room, bathrooms or storage rooms.

A closet comes under the placement rules, since it is an enclosed space.

Read the questions people ask about running a test.

Keep it at breathing height, off the floor and away from exterior walls

Put the detector at least 30 cm above the floor, within the breathing zone of 0.3 to 2.5 m. Keep it at least 30 cm from walls and ceilings and 10 cm from other objects. It must not touch the floor, the ceiling or an exterior wall.

Do not put it in an enclosed space such as a closet or drawer. Choose a spot where it will not be moved. C-NRPP’s guidance for consumer monitors says to read the manual, since placement guidance and averaging differ between devices. Place the monitor in a room occupied at least four hours a day.

See which test kits and monitors are listed.

Keep it clear of windows, doors, vents and heat sources

Keep the detector at least 1 m from vents, windows, doors or anything else that interferes with airflow. Keep it out of direct sunlight and away from any heat source. Manufacturer operating ranges in the guide are 0 to 35 °C, relative humidity below 80% and pressure of 70 to 110 kPa.

The test still runs 91 days or more, from 3 to 12 months, with at least 91 days in the heating season.

Find out how long to test and when.

Keep it away from electronics and from entry points like sumps and foundation cracks

Keep the detector away from electronic and network devices. Keep it away from sump holes, crawl spaces and exposed foundation cracks.

Health Canada names placement that strays from the guidance as one of four conditions that weaken a result. The other three are a test under 91 days, a damaged or tampered device, and fewer than 91 days in the heating season. The result is compared with Health Canada’s guideline of 200 Bq/m³ for the average annual level in a normal occupancy area.

Find out what the number means once the test is done.

How to work it out by hand

The tool applies Health Canada’s placement rules in a fixed order, and you can follow the same steps without it.

1. Find the lowest level of your home with a room someone uses more than four hours a day.
2. Pick a bedroom, family room, living room, den, playroom, office, basement workshop or basement apartment on that level, not the kitchen, bathroom, laundry or storage room.
3. Put the detector at least 30 cm above the floor and at least 30 cm from walls and ceilings.
4. Keep it at least 1 m from windows, doors and vents, and at least 10 cm from other objects.
5. Keep it out of enclosed spaces, out of direct sun, away from heat sources and away from electronics.
6. Keep it away from sump holes, crawl spaces and exposed foundation cracks.
7. Leave it where it is for the whole test.

See how the Index checks its numbers and dates.