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Before The Alarm Sounds

Published in Canadian Property Management: GTA & Beyond magazine  

By Steven Strege, PE

Fire, egress models allow building design to move beyond applicable code requirements

With the advancement of computers, mathematical models have emerged to aid engineers and architects in the design of safe buildings. A prime example of this is in the area of fire safety.

Fire protection systems and egress components of a building must meet prescriptive fire code requirements, unless it can be demonstrated that the building design meets an equivalent or higher level of safety through a performance-based design. This option was first introduced 15 years ago in the 2000 edition of the National Fire Protection Association’s (NFPA) Life Safety Code, known as NFPA 101.

FIRE RISK ASSESSMENT
Computer models provide an invaluable tool to evaluate the level of safety provided by a performance-based design. Fire protection engineers use two types of models: Fire models and egress models. Fire models are used to predict the growth of a fire (producing heat and smoke) and its impact on the building’s environment. Egress models are used to predict the movement of people and how long it will take to evacuate the building or space within the building.

Fire and egress models are often used together to assess the environmental condition that will develop from a fire and the time required to evacuate occupants to an area of safety before an untenable condition occurs due to heat and smoke. For example, fire and egress models are typically used in smoke control design via a tenability analysis. A modelling analysis of a proposed smoke control system, for example, may show occupants will be exposed to light (yet tenable) smoke during an evacuation event. Conversely, under prescriptive codes, exposing occupants to any level of smoke is not permitted since the properties of the smoke are unknown and, therefore, worst-case conditions must be assumed.

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