Radon gas is colorless, odorless and tasteless radioactive gas. It is formed by the breakdown of uranium, a natural radioactive material found in soil, rock and groundwater.
Radon gas escapes from the ground into the outdoor air. It is diluted to low concentrations and is low concern. However, radon that enters an enclosed space, such as your home, can sometimes accumulate to high levels. Radon gas breaks down to form additional radioactive particles called “progeny” (Polonium-218, Lead-214, Bismuth-214, Polonium-214) that can contaminate the air you breathe.
Concern in Canada about indoor radon gas levels began in the mid-1970s. Some houses in communities where uranium ore was either processed or mined were found to have high radon concentrations. After this discovery, Canadian Government surveyed the radon levels in 14,000 houses in 18 cities across Canada. Also, some smaller communities have been identified by provincial government agencies as having the potential for high radon concentrations in dwellings.
The majority of homes surveyed showed low concentrations of radon gas. However, significant minority of houses in some locations were found to have very high levels of radon gas.
Source: RADON: A Guide for Canadian Homeowners