Concrete-block walls are particularly porous to radon. Radon trapped in water from wells can be released into the air when the water is used. A survey conducted in the late 1970s by Health Canada showed that radon levels in certain Canadian cities were higher than in others. However, measurements have been made in thousands of houses in Canada, and so far it has not been possible to predict whether any one house will have a high radon level or not. Factors such as the location of a house and its relation to the prevailing wind may be just as important as the source of the radon.
Commercial services are available to homeowners who wish to measure radon levels in their homes.
There are several different ways to measure radon in a house. The most popular commercially available radon detectors are the charcoal canister and the alpha track detector. Both of these devices are exposed to the air in a house for a specified period of time and sent to a laboratory for analysis. There are other techniques, which require a trained operator, but such techniques are more expensive. In Canada the provincial governments have jurisdiction over the health effects of background radiation, but the federal government has proposed guidelines to the provinces for their consideration.