Fire Safety Should Not Suppress Design
The role of the fire protection engineer (FPE) is to assist project managers in the design of efficient and cost-effective fire protection and alarm systems that protect both people and buildings. FPEs also evaluate a building’s condition in order to access its level of fire safety and are heavily involved in writing the many codes and standards that affect nearly every aspect of the construction industry.
These engineers are well versed in the fire-safety related architectural requirements that often drive the building’s layout. They design systems such as automatic sprinklers and they design fire alarm systems based on sophisticated electrical circuitry. They also specify the fire resistance necessary to protect a building’s structural components.
Performance-Based Design
In the prescriptive approach to construction, building codes dictate how a building will be built-it is essentially a "one-size-fits-all" approach. The prescriptive approach is useful because requirements are easily enforceable and, when well written, fairly obvious. The downside to the prescriptive approach is that most buildings have unique design features or function in ways not yet properly addressed by codes. Building codes are typically developed in three-year cycles and do not always accommodate the latest technologies.
In performance-based design, FPEs have developed a new generation of analytical tools that allow them to evaluate a specific building and its own unique capacity for withstanding a fire. Performance-based design can be used to explore varied architectural designs while tailoring fire- and life-safety systems to a specific building. This arrangement can help reduce costs by eliminating unnecessary fire-protection features by identifying and protecting against actual potential hazards in a building. However, reducing the cost of construction is not always the result.
Imagine a K-12 school in an old, inner-city building. The school has been in operation for more than 50 years and has been well maintained, but never really updated. Now, the building is about to undergo a complete renovation and modernization and it will have to comply with all the requirements of modern building codes. How is that possible when the building has several unenclosed grand stairs, no sprinkler or fire-alarm system, insufficient exit capacity, and many dead-end corridors?
Evaluation
At this point there are several options for dealing with the old school’s new plans. The first is to proceed with the renovation and hope that none of these deficiencies is identified by the building code official or fire marshal. This solution only appeals to those who feel that unsafe buildings are acceptable. The second option is to comply with all requirements of the building code regardless of cost and impact on aesthetics and functionality. This option will provide you with a building that meets code but lacks the efficient use of space demanded in today’s schools. The impact of this solution becomes obvious when the building’s functionality is reduced and classrooms are eliminated because existing stairs are enclosed, new corridors are created, and additional stairs and exits are added. These changes occur without any assurance that the new features are effective fire-safety measures. In many renovations, this approach defeats the supposed benefits of the renovation.
A third option is to evaluate the building in a performance-based design approach. This evaluation establishes a baseline level of safety within the building for a wide range of fire scenarios. It can then be determined which additional fire-protection features (sprinklers, automatic fire detection, enclosure of specific critical stairs, etc.) are necessary to ensure the code-intended level of safety is reached, without providing unnecessary fire-safety measures.
To conduct the analysis, computer-based evacuation modeling is used in conjunction with the fire modeling to determine if the paths of egress within the building will be remain free of untenable levels of smoke and hot gases from a fire. The quantity of smoke and hot gases are tracked by the fire model to predetermined performance criteria, such as the maximum permitted temperature from the fire, the maximum smoke concentration, or the maximum concentration of carbon monoxide. Results should demonstrate that at no point during the time necessary to evacuate the building was the threshold criteria for carbon monoxide concentration, smoke concentration, or temperature reached or surpassed. Results are obtained using conservative ranges for the design fires (i.e., worst-case scenarios), occupant loading and egress characteristics, and performance criteria.
Information on the Society of Fire Protection Engineers can be found at www.sfpe.org.
Andrew Bowman, P.E., is a senior fire protection engineer with Gage-Babcock & Associates and a member of the Society of Fire Protection Engineers. He can be reach at abowman@gagebabcock.com.