|Approaches to Designing Fire Safety in Buildings|
From the Technical Director:
Approaches to Designing Fire Safety in Buildings
By Morgan J. Hurley, P.E. | Fire Protection Engineering
Fire protection is typically designed into buildings to achieve one or more fundamental goals: 1
Life Safety. This goal includes mitigation of injury or death caused by fire to the public, building occupants and members of the fire brigade.
Property Protection. Property protection goals address protection of building contents, historical features and the building itself from fire.
Business Continuity. Business continuity goals are associated with ensuring that an organization can continue to operate following a fire. Meeting business continuity goals may require protection of production or manufacturing operations, critical supplies or other operations essential to an organization's mission.
Environmental Protection. Providing environmental protection from fire requires designing such that the fire or runoff from fire-fighting operations does not harm the environment. For most buildings, goals will be stipulated by the applicable building code. The goals identified in building codes vary somewhat by country. Codes in all countries provide life safety and property protection as goals; however, the degree of property protection differs among countries. Environmental protection is generally only a consideration for buildings that contain hazardous chemicals. Continuity of operations is typically only regulated to the extent that it affects the public well-being for example, in buildings such as hospitals that provide critical public services. In other buildings, protection of mission is only addressed by the building owner, tenant, or insurer, and is not addressed by building codes.
There is a multitude of ways in which fire protection can be designed such that these goals are achieved. In many buildings, fire safety is achieved through a combination of "active" and " passive" systems. "Active" systems are those that take an action to control a fire. Examples of "active" systems are sprinkler systems, fire alarm systems and smoke control systems.
"Passive" systems are systems that are in place before a fire and require no action to mitigate the effects of fire. Examples of " passive systems" include structural fire resistance and compartmentation.
As with fire safety goals, the approach that is commonly taken to fire protection differs somewhat from country to country; however, fire safety approaches can differ more than goals do. For example, many European and Asian countries emphasize the use of smoke control systems and passive fire protection strategies to achieve fire protection goals.
Other countries take different approaches to fire safety. In North America, active systems such as sprinklers and fire alarms are used more frequently than in Europe or Asia. Other types of systems, such as compartmentation, structural fire resistance and smoke control, are also used, although their use is generally only required in specific types of buildings. Of course, some buildings do not use either active or passive fire protection systems.
One reason that approaches to fire safety differ, is that building codes have evolved differently. A motivation for changing prescriptive building codes is the occurrence of fire events that have an unacceptable outcome. Following a fire that has an outcome that is unacceptable, building codes are modified to prevent similar events from occurring in the future. However, if the incident that precipitated the change to the building code is not international in significance, codes in other countries will probably not be modified. Other factors can also influence the evolution of prescriptive codes, such as the availability of locally developed systems or technologies.
The measure of acceptability of prescriptive codes is generally based on fire losses if the fire losses associated with a prescriptive code are acceptable to society, the code is considered sufficient. Therefore, although prescriptive codes may vary with geographic area, one code is not necessarily superior to another.
As performance-based codes become more widely used, fire safety designs will still generally differ among geographic areas because designers and code officials will tend to select strategies with which they are familiar. Different types of designs will be used in cases where unique fire hazards dictate specialized solutions. Additionally, multinational companies (e.g., hotels) will endeavor to have their properties as similar as possible, and hence will push for fire safety designs that are as alike as possible.
With performance-based designs, the measure of acceptability is whether or not the design team can demonstrate to the satisfaction of the code official that the fire safety strategy that they select achieves the fire safety goals. This will allow designers and building owners more flexibility. However, designs will likely not differ tremendously from those that have been traditionally used.
The ultimate measure of acceptability of the fire safety designs, whether it is based on prescriptive code requirements or performance-based engineering, is fire losses. If the fire losses associated with local codes are acceptable, the code and design process is considered sufficient.
1SFPE Engineering Guide to Performance-Based Fire Protection, National Fire Protection Association, Quincy, MA, 2006.