Radon is a radioactive gas that is formed naturally by the breakdown of uranium in soil, rock and water. It cannot be detected by the senses due to its colourless and odourless properties; however, it can be detected with special instruments. Radon usually escapes from the ground into outdoor air where it mixes with fresh air resulting in concentrations too low to be of concern. However, when radon enters an enclosed space, such as a building, it can accumulate to high concentrations. The only known health risk associated with exposure to radon is an increased risk of developing lung cancer. The level of risk depends on the concentration of radon and length of exposure. Radon gas is the second leading cause of lung cancer after smoking. While radon is the second most frequent cause of lung cancer, it is the number one cause among non-smokers, according to EPA estimates.
Because the source of most radon in homes is the soil on which the house or building is standing; Common entry points are cracks in the foundation, poorly sealed pipes, drainage or any other loose point. Radon that escapes from the soil and infiltrates a home tends to be heavier than air. Higher indoor radon levels are more likely to exist below the third floor. For this reason Health Canada recommends testing all homes below the third floor. In some cases, higher radon levels have been found at or above the third floor, due to radon movement through elevators or other air shafts in the building. If your apartment is at or above the third floor and you are concerned about this possibility, you could also choose to test for radon.
Although there is no regulation that governs an acceptable level of radon in Canadian homes or public buildings (considered as “dwellings”), Health Canada, in partnership with the provinces and territories, has developed a guideline. This guideline provides Canadians with guidance on when remedial action should be taken to reduce radon levels.The following guideline was approved by the Federal Provincial Territorial Radiation Protection Committee in October 2006 and adopted by the Government of Canada on June 9, 2007:
“Remedial measures should be undertaken in a dwelling whenever the average annual radon concentration exceeds 200 Bq/m3 in the normal occupancy area.
The higher the radon concentration, the sooner remedial measures should be undertaken.
When remedial action is taken, the radon level should be reduced to a value as low as practicable.
The construction of new dwellings should employ techniques that will minimize radon entry and will facilitate post-construction radon removal, should this subsequently prove necessary.”
Radon Testing and Mitigation
There are relatively simple tests for radon gas. Testing for radon can be accomplished in two forms: active and passive. Active devices constantly measure the levels of radon in a portion of the home and display those results. Passive devices collect samples over a period of time and then are taken away and analyzed. Either method can help you determine your level of risk. The short-term radon test kits used for screening purposes are inexpensive and are commercially available. The kit includes a collector that the user hangs in the lowest livable floor of the house for 2 to 7 days. The user then sends the collector to a laboratory for analysis. Long term kits, taking collections for up to one year, are also available. Radon levels fluctuate naturally, due to factors like transient weather conditions, so an initial test might not be an accurate assessment of a home’s average radon level. Radon levels are at a maximum during the coolest part of the day when pressure differentials are greatest. Therefore, a high result over 200 Bq/m3 justifies repeating the test before undertaking more expensive abatement projects.
Generally, the indoor radon concentrations increase as ventilation rates decrease. In a well-ventilated place, the radon concentration tends to align with outdoor values (typically 10 Bq/m3, ranging from 1 to 100 Bq/m3).
Radon levels in indoor air can be lowered in a number of ways, from sub-slab depressurization to increasing the ventilation rate of the building. The four principal ways of reducing the amount of radon accumulating in a house are:
- Sub-slab depressurization (soil suction) by increasing under-floor ventilation;
- Improving the ventilation of the house and avoiding the transport of radon from the basement into living rooms;
- Installing a radon sump system in the basement;
- Installing a positive pressurization or positive supply ventilation system.
The primary method to reduce radon levels in residential homes is a vent pipe system and fan, which pulls radon from beneath the house and vents it to the outside, which is also known as sub-slab depressurization, active soil depressurization, or soil suction. Generally, indoor radon can be mitigated by sub-slab depressurization and exhausting such radon-laden air to the outdoors, away from windows and other building openings.
Positive-pressure ventilation systems can be combined with a heat exchanger to recover energy in the process of exchanging air with the outside, and simply exhausting basement air to the outside is not necessarily a viable solution as this can actually draw radon gas into a dwelling.
For more information see Bill 182 or visit Health Canada website http://www.hc-sc.gc.ca/index-eng.php