Balancing passive, active fire protection
Fire protection engineers should consider the building's construction, fire suppression systems, and smoke control when designing active and passive fire protection systems.
- Explain the International Code Council (ICC) and NFPA's elements and integration of both passive and active fire protection to reinforce one another.
- Assess the differences between active and passive fire protection systems and learn which codes pertain to these systems.
For more than 2 decades, the concept of balancing passive and active fire protection has been debated in the code-development hearings in the United States, including the International Code Council (ICC), NFPA, and legacy code organizations. Typically, there are proposals to require sprinkler protection in certain buildings and, in many instances, there is an attempt to offset the cost by reducing or eliminating one or more passive fire protection features.
In some instances, the sprinkler protection may already be required and fire data is used in an attempt to substantiate the reduction or elimination of one or more passive fire protection features. While there are other forms of active fire protection, sprinkler systems seem to be at the forefront of the discussion regarding balanced fire protection.
A historic perspective of balanced fire protection
As evidenced by the testimony at code-development hearings, some people define balanced fire protection as "one of everything." One of everything could include sprinklers, automatic detection, and fire-resistance-rated construction. Others may not promote the concept of one of everything. Rather, they will support retaining existing passive fire protection feature requirements due to the fact that the active fire protection feature is not 100% reliable.
However, the word "balanced" can be defined as being in proper proportion. For the purposes of this article, the concept of proper proportion will be used in trying to define the phrase "balanced fire protection."
There have been code-change proposals submitted to eliminate a passive fire protection feature in an area in which sprinkler protection is not even provided. For example, proposals have been submitted to eliminate draft-stopping in a combustible attic space if the building is protected throughout with an automatic sprinkler system complying with NFPA 13R: Standard for the Installation of Sprinkler Systems in Low-Rise Residential Properties, even though sprinklers are not provided in the attic space. While an NFPA 13R sprinkler system certainly may reduce the number of fires that spread to the attic space, should the fire start in the attic space—or spread to the attic despite the sprinkler system—there would be no protection feature in the attic space to offset the omission of the draft-stopping. One might argue that such a provision does not offer balanced fire protection.
With respect to balanced fire protection, it may be less clear when a prescriptive requirement for a 1-hour fire barrier or 1-hour fire partition is reduced to a nonrated assembly due to the presence of an automatic sprinkler system. Prior to requiring sprinkler protection in all new hospitals, codes generally required a 1-hour corridor if the building, or smoke compartment, was not protected with sprinkler protection.
Those same codes often reduced the corridor-wall requirement to an assembly capable of "resisting the passage of smoke" if the building, or smoke compartment, is protected with an automatic sprinkler system.
Consider these ideas to determine whether the fire protection system is in balance: If a fire occurs in the building protected with a sprinkler system, what happens if the wall is not capable of resisting the passage of smoke due to some compromise in the integrity of the wall? As a separate consideration, what happens if the sprinkler system fails to effectively control the fire? If a fire occurs in the building that is not protected with a sprinkler system, what happens if the 1-hour fire partition is compromised? Does the code have a proper proportion of passive and active fire protection? Are there any tools to assist in answering these questions?
Passive and active fire protection features often complement each other. For example, John R. Hall Jr., PhD, noted in his report, High-Rise Building Fires, that the U.S. experience is such that there is a lower risk of fire and associated losses in high-rise building fires than in other buildings of the same property use. He noted that this experience is most likely due to the increased presence of sprinkler protection and fire-resistance-rated construction in high-rise buildings.
NFPA 550: Guide to the Fire Safety Concepts Tree was developed by the NFPA Committee on Systems Concepts. The committee was established to be responsible for developing system concepts and criteria for fire protection in buildings. The committee subsequently was discharged in 1990 and the responsibility for NFPA 550 was reassigned to the NFPA Standards Council. With the exception of updating reference standards, there have been essentially no technical changes to the guide since the first edition. Obtain free access to the 2012 edition of the code and graphics at www.nfpa.org/550.
At the top of the Fire Safety Concepts Tree in Chapter 4, the "or" gate indicates that the desired fire safety objectives can be achieved by either preventing the fire or managing the fire. For purposes of this article, the focus will be on the "Manage Fire Impact" branch of the tree. Note that this branch contains two offshoot branches connected by an "or" gate: "Manage Fire" and "Manage Exposed." The objectives of the Manage Fire branch are to reduce hazards related to fire growth and spread, thus reducing the impact of the fire. The Manage Exposed branch includes coordination involving the items specified in the fire safety objectives, such as people, property, or other valued items.
The Manage Fire branch then contains three more branches: "Control Combustion Process," "Suppress Fire," and "Control Fire by Construction." Whereas all of the branches identified are connected by an "or" gate, if one is able to be 100% effective with any of the branches, the others are not needed.
Fire experience in the United States has indicated that we are not 100% successful with either of the two major branches of the tree, with the two branches under Manage Fire Impact, or with the three branches within the Manage Fire branch. Therefore, prescriptive codes generally contain requirements related to preventing fires, controlling the combustion process, suppressing the fire, controlling the fire by construction, and managing those exposed to the fire.
The remainder of the article will focus on proportioning or balancing the Suppress Fire and Control Fire by Construction branches. However, before we continue with these two branches, it should be noted that passive fire protection features and active fire protection systems also play a role within the Manage Exposed branch of the tree.