Radon is a clear, colourless, radioactive gas. It is generated by the radioactive decay of naturally occurring uranium in soil and bedrock. Radon in your home can be a problem. It is the second leading cause of lung cancer in Canada.
Any discontinuity in the foundation wall or slab presents a potential entry point for radon.
Radon intrusion is generally the greatest during the heating season. Warm air in the building rises drawing replacement air (potentially from subsurfacel) behind it. This stack effect, and closed building conditions during the heating season is why Health Canada recommends a long term test (minimum 90 days) between October and April.
It is the radioactive decay of radon that poses health issues. The decay of radon is measured in units of bequerels (Bq). A bequerel is one decay per second. The more radon, the higher the decays, the higher the bequerels. Health Canada has indcated that remedial measures should be undertaken where the radon concentration exceeds 200 Bq/m.