The National Building Code of Canada permits natural pressurization to be used as a smoke management mitigation measure for stair cores serving floors above the lowest exit level within ‘high’ buildings. A predominant supporting rationale behind the natural pressurization method is cold weather experienced within Canada during the winter months. Considering the impact of climate change, impact of construction variables, and drive for thermally efficient buildings, the efficacy of pressurization to perform to a minimum standard should be re-examined. Research has subsequently been conducted to explore the appropriateness of this prescriptively compliant, deemed-to-comply solution and the subsequent reliability.

The fundamental principles that underpin fire safety are predominantly universal irrespective of where in the world a building is designed. The primary premise being that fire precautions are assigned to a building based on a considered risk profile.
A significant component of the approach to Canadian, and global, fire safety is the management of the increased risk posed to the occupants and firefighters presented by high buildings. The risk is manifested by an increased distance for evacuation, increased risk of smoke transport to upper floor levels, and the reduction of external firefighting capabilities. This reliance on the building infrastructure to support occupants and firefighters imposes a greater emphasis on fire precautions to mitigate risk to tolerable levels.

A fundamental component of high-building measures is the protection of exit stairs. In Canada, the national building code imposes “Limits to smoke movement” that informs how stairways are protected. Canada has adopted an approach that allows natural pressurization to limit smoke movement to all exit stairways that serve floors above the lowest exit levels irrespective of height for high buildings. This approach for natural pressurization purely relies on an openable vent and a variance in internal and external temperature to mitigate smoke spread and protect escaping occupants and firefighters.
The adoption of natural pressurization has placed a heavy impetus upon stack effect and the ability to control the neutral pressure plane that is historically supported by the sustained winter temperatures experienced in Canada. This approach is unique to Canada with other international building regulation documents levying significantly higher levels of performance for comparable stairway protection in high buildings.
This presentation serves to:

1. Explore the theoretical efficacy of a natural pressurization system as a smoke management risk mitigation measure within a high building exposed to various Canadian climates.
2. Model and quantify the expected performance of a natural pressurization system utilizing computational software (CONTAM).
3. Comment on the reliability and confidence of such a system with contemporary understanding of fire dynamics and the evolving built environment.
4. Rationalize the expectations of this deemed-to-comply solution in respect to implicit risk within the regulatory framework.