Radon is a radioactive gas that occurs naturally in soil. It's part of the breakdown of uranium as it decays down to lead.
Radon is invisible, you can't smell it, and the only way to know if it's seeped into your home through a test.
The Canadian lung association says when inhaled, tiny radioactive particles given off by the decay of radon can damage the cells that line the lungs and long term exposure can lead to lung cancer.
"In the winter when the ground was frozen solid it might be wet underneath and your house is warm inside. That's where that pressure can change and get into your home," says Brody Todd of Radon Atlantic.
If high levels of radon are detected in your home, installing a radon mitigation system can reduce your levels dramatically by blowing the radon outdoors.
Radon detectors can be purchased from your local lung association.