Selecting a fire protection system
Understanding agent characteristics, limitations
As referenced above, various types of firefighting agents are available for achieving fire safety goals. They can take the form of liquids, solids, and gases. However, each agent—whether an aqueous solution, inert gas, or chemical powder—possesses certain characteristics and limitations that must be understood by the design engineer. For example, clean agents, while stored in a highly pressurized liquid state, are applied in a gaseous form that is electrically nonconductive and leaves no residue. Gases or vapors are better suited to suppress fires in the presence of physical barriers or obstructions. However, the extinguishing or inerting concentration of particular gaseous agents needs to be held for a specified period of time, and successful extinguishment is tied to the integrity and ventilation aspects of the enclosure in which the agent is discharged. Upon release of the agent, if complete extinguishment of the fire does not occur within the specified hold time, the fire is likely to rekindle and continue to spread, unless a redundant system or other strategy is in place.
When considering a specific agent and accompanying system, the following factors warrant consideration: What is the agent’s effectiveness and compatibility with the types of fuels and fires expected—ordinary combustibles, flammable liquids, and so on? Can the agent be discharged on electrically energized equipment? Will the discharged agent leave a residue or otherwise impact the equipment or contents it is designed to protect? Does the agent decompose in the presence of the fire or heat and affect the components to be protected? Are there health or environmental concerns with agent discharge? Should the agent be reclaimed or otherwise contained after discharge? What are the costs for the overall system including maintenance? How quickly can the system be recharged? Has compatibility of system operation with facility operations been sufficiently considered? Does system operation require specialized training of building staff and emergency responders?
Planning for long-term performance
When deciding on those fire protection systems that best serve the intended fire and life safety purposes, the long-term effectiveness and performance of the systems need to be incorporated into the decision-making process. Once the systems are commissioned, the occupancy certificate is issued, and the building is in operation, the design team moves on. It is now the owner’s responsibility to keep the building and the respective fire and life safety systems in proper working order. The applicable fire code, which normally applies to existing buildings, will address the need to maintain an appropriate level of safety. This should translate to an effective inspection, testing, and maintenance program for the installed fire and life safety systems. Details of this program should be incorporated into the early stages of the system selection and design process, as it will have a distinct impact on the building’s overall operational costs.
Most design and installation standards contain some information about the necessary inspection, testing, and maintenance activities. For instance, NFPA 2001 includes a chapter entitled “Inspection, Testing, Maintenance, and Training.” However, these provisions can be generic in nature. When it comes to specific types of proprietary or pre-engineered systems, the design, installation, and operation manual furnished by the system manufacturer should be obtained and evaluated before any system is selected. While these manuals tend to be tailored for each individual system installed, sample manuals for the types of applications under consideration can be requested and made available.
Designing the system to facilitate the work of inspection, testing, and maintenance personnel, as well as contemplating the availability of replacement parts and system supplies, should receive proper priority. Designing the system to best facilitate testing and maintenance activities is not necessarily a provision mandated by the applicable design and installation standard, but doing so will help ensure more cost-effective long-term performance of the system.
Additionally, if replacement parts and supplies are not readily available but are needed, the resulting disabled or impaired system means that life safety and the owner’s investment are unduly compromised. While not within the scope of routine inspection and maintenance, future building expansion and anticipated changes in building operations also deserve attention. Can the fire protection system once installed be expanded or otherwise modified to address the related change in fire hazard, or will an entirely new replacement system be necessary?
Making the recommendation
Providing the appropriate fire protection systems for your client will often require more than just code consulting and compliance with the applicable regulations. A comprehensive fire and life safety strategy needs to be developed and implemented with the overall long-term goals of the building owner clearly articulated, agreed upon by the relevant stakeholders, and properly documented. A competent fire safety analysis and assessment will facilitate the overall strategy, identify the applicable regulations to adequately serve the fire and life safety needs of your client over the expected life span of the building or structure, and more effectively address any gaps in protection.
The fire protection engineer needs to be knowledgeable and well-versed with the application and limitations of all the different types of fire protection systems that could be used to satisfy the overall fire and life safety goals and objectives for the project. This requires not only an unbiased in-depth grasp of the applicable rules, regulations, available technologies, design principles, and testing protocols, but also a sufficient understanding of the operations for the planned building and the associated fire and life safety risks. As noted above, a comprehensive application guide addressing the numerous types of fire protection systems does not exist.
So, with all the factors that can come into play, are you prepared to make the recommendation?
Milosh Puchovsky is professor of practice at Worcester (Mass.) Polytechnic Institute’s department of fire protection engineering and a member of numerous NFPA Technical Committees. He is a registered professional engineer possessing 25 years of experience in the field focusing on the performance of fire protection and life safety systems. He also serves on the bBoard of SFPE and is the former secretary to NFPA’s standards council.