After smoking, radon exposure is the next leading cause of lung cancer. According to Health Canada, it is responsible for approximately 16 per cent of the country’s lung cancer deaths, claiming around 3,200 lives every year.

Radon is a naturally occurring radioactive gas caused by the breakdown of uranium in soil, rock and groundwater. The gas deteriorates into radon decay products (RDPs), which, when inhaled, can adhere to lung tissue and emit high-energy alpha radiation particles that can damage cells and increase the risk of lung cancer.

Present at extremely low levels in outdoor air, radon can become a problem if it accumulates to elevated levels inside a building. Radon can potentially enter a building at any point where it is in contact with the subsurface soil or rock, including through cracks, sumps, floor/wall joints or unfinished floors in crawlspaces. Testing is the only way to detect elevated indoor levels of the invisible, odourless, tasteless gas.

Here’s what condo boards and managers need to know about testing for and mitigating high radon levels.

Radon testing

There are two general categories of tests to measure radon: short-term tests (typically lasting 48 hours to seven days) and long-term tests (ranging from 91 days to one year). Radon levels in a building can vary significantly from hour to hour, day to day and even more so from season to season. Given these variances, long-term tests are better at estimating the annual average radon concentration in a building. Health Canada says that decisions for radon mitigation should be based on the result of a long-term radon test.

For occupied areas/rooms of buildings, Health Canada has set 200 Becquerels per cubic metre (Bq/m³) as as the action level for mitigation. The term ‘occupied’ refers to those areas/rooms which are occupied by an individual for more than four hours per day.  If radon levels exceed 200 Bq/m³ but are less than 600 Bq/m³, Health Canada recommends mitigating the radon within two years. If levels exceed 600 Bq/m³, Health Canada recommends mitigating the radon within one year.

Mitigation strategies

In buildings without a robust mechanical ventilation system, the most common and effective way to mitigate radon is to install a sub-slab depressurization (SSD) system.  An SSD system draws air from beneath the building and exhausts it to the outdoors where it is diluted to safe levels. If a building has a robust mechanical ventilation system, the system can potentially be manipulated to dilute indoor radon concentrations and/or pressurize a building to essentially ‘push’ the radon out.

Efforts to limit indoor radon levels in newly constructed buildings are underway. Specifically, the 2010 National Building Code (NBC) defines requirements for Readily Remediated New Construction (RRNC).

These requirements not only limit radon entry into a building, but also make it simpler to mitigate radon concentrations after a building has been constructed. Examples of these provisions include installing an airtight sump pit cover, caulking the slab perimeter and penetrations, placing granular fill and a soil gas membrane under the slab as well as roughed in piping for an active SSD system, if required.

The radon-related aspects of the NBC have not been widely adopted in new construction in Canada. However, given the health risks of high indoor radon levels, it’s no surprise that more and more municipalities across the country are starting to implement them.

Owners and managers of existing buildings can reduce their risk by following Health Canada’s guidelines for testing and mitigating high radon levels indoors. If assistance is required, be sure to work with a certified radon professional. Health Canada and the Canadian Association of Radon Scientists and Technologists (CARST) have established the Canada National Radon Proficiency Program (C-NRPP), which certifies and licenses professionals. Local professionals are searchable on the C-NRPP website.

Scott Cryer (P.Geo.) is an operations manager with the Hazardous Materials group at Pinchin’s Mississauga, Ontario office. He is also certified with the Canadian National Radon Proficiency Program (C-NRPP) as a radon measurement and mitigation provider and a director with the Canadian Association of Radon Scientists and Technologists (CARST).