Radon levels in a home change significantly over time. They can rise and fall from one hour or day to the next and seasonally. Radon concentrations are usually higher in winter than in summer, and are usually higher at night than during the day. This is because the sealing of buildings (to conserve energy) and the closing of doors and windows (at bedtime), reduce the intake of outdoor air and allow the build-up of Radon. For this reason, measurements taken over a longer period of time are more accurate.
You can either purchase a do-it-yourself Radon test kit from your local hardware store or from a local community organization or you can contact a Canadian National Radon Proficiency Program (C-NRPP)-certified Radon Measurement Professional in your area.
Health Canada recommends that home owners do a long-term radon test, for a minimum of three months, during the fall or winter months and that the detector is placed in the lowest level of the home (where homeowners spend a minimum of 4 hours per day). A three-month test represents a person’s annual average exposure and should be used to determine if a home’s radon concentration exceeds the Canadian guideline level of 200 Bq/m3.
The long-term radon detectors most commonly used in Canada are:
Alpha Track Detector
These detectors use a small piece of special plastic enclosed in a container. The detector is exposed to the air in a home for a specified time. When the radon in the air enters the chamber, the alpha particles produced by decay leave marks on the plastic. At the end of the test the detector is returned to a laboratory for analysis, and the average radon concentration is calculated.
Images of alpha track detectors
Electret Ion Chamber
This detector contains a disk called an “electret,” which has an electrostatic charge housed in a container. When the detector is exposed to the air in a home for a specified time, the radon in the air enters the container and the ionization produced by decay reduce the electret charge. The difference in the charge is measured by a specialized voltmeter, and from that the average radon concentration is calculated. This can be done in the home, or the detector can be returned to a laboratory for measurement.
Images of electret ion chambers
When you need a fast measurement of the Radon concentration – for example, to check how a mitigation system is working – a short-term measurement of two to seven days is acceptable. However, short-term measurements should never be used to determine if the Radon concentration in a home exceeds the Canadian Guideline or to assess the need for remedial actions. The result of any short-term measurement should be confirmed with a follow-up long-term measurement made at the same location.
Digital Radon Monitors for short- and long-term testing are also available on the market, however, Health Canada can not recommend their use because they have not yet been evaluated and approved by the Canadian National Radon Proficiency Program (C-NRPP).
Measuring Radon concentrations in larger buildings (such as office buildings or schools, hospitals, etc) follows a similar procedure but may require more test devices. If you live in an apartment building and wish to test for Radon, it’s best to speak to your landlord first. Be sure to communicate your concerns about Radon and think about your willingness to share costs of testing or reduction methods if necessary.
More information on Radon measurement can be found in Health Canada’s Radon measurement guides for homes and public buildings.
Click here to find a radon test kit in your local province.