CAN/CGSB 149.12-2024 PDF

This National Standard of Canada provides details on two types of radon mitigation system that can be selected based on the conditions present in and around an existing building.

Active soil depressurization (ASD) systems – ASD systems utilize a fan to create negative pressure on the soil side relative to the interior of the building and exhaust the radon-laden soil gas to the outdoors where it is rapidly diluted. ASD systems can provide a reduction of indoor radon gas concentrations of approximately 90% or more when systems are properly designed and installed by certified professionals. ASD is the preferred method of reducing radon in a building, when practical and installed according to this standard and best practices. It has been shown to be able to reduce radon levels significantly and it is simple and easy to maintain.

Ventilation systems – Reduction of radon gas concentrations in a building can also be achieved through dilution of indoor air using balanced ventilation systems as provided by example systems such as a heat recovery ventilator (HRV) or an energy/enthalpy recovery ventilator (ERV). Balanced ventilation systems in airtight buildings have been shown to reduce indoor radon gas concentrations by an average of 20 to 50%. Ventilation can be used as a supplemental option or in certain circumstances, where ASD systems are not practical. Ventilation effectiveness can be influenced by several factors of building use and can decline in effectiveness if not properly maintained, and therefore should include a system where radon levels are continuously monitored.

When applying either mitigation technique, sealing of the slab and other entry points for radon gas is necessary.

Units of measurement – Quantities and dimensions used in this standard are provided in units from the International System of Units (SI units). Imperial equivalents may be shown in brackets, if applicable.