Medical News Today reports that Health Canada is proposing a revised guideline for indoor radon gas levels that is four times more stringent than the one now in place. Radon is a colorless, odorless, radioactive gas that occurs naturally in the environment. Normally it does not pose a health risk, but in confined, indoor spaces, radon can easily become a health hazard.

Radon is the number one cause of lung cancer after cigarette smoking. HEPA air purifiers with activated carbon filters reduce radon levels.