Selecting a fire protection system
Fire protection engineers must know what factors come into play when deciding on and recommending a fire protection system.
- Understand the factors to consider when determining the need for specific types of fire protection systems.
- Learn how codes, standards, and other documents influence the choice of fire protection systems.
- Identify the importance of goal setting, loss tolerance, and the application of risk assessment techniques in deciding on fire protection systems.
A principal role of the consulting engineer is the design of building systems that satisfy the overall goals and objectives of his or her client. When it comes to fire and life safety, the fire protection engineer is called upon to design those systems deemed necessary for the project.
Several questions might be posed: What systems are necessary? Is one type of system or systems more appropriate than another? Are redundant systems needed? Who makes this decision and recommendation, and what influences their thought process?
Associating client goals with building, fire regulations
Any building project is a significant investment and undertaken with specific goals and outcomes in mind. Once built, the structure serves the purposes and needs of its owners. The building and its associated systems enable the operations of the overall enterprise contained within, that is, provide a workplace, facilitate healthcare services, support manufacturing processes, shelter people and assets, and so on.
To ensure that fire and life safety features are sufficiently considered and provided for in the design and construction of a building, governmental regulations come into play and must be adhered to. Therefore, one of the principal needs and goals of the building owner is identification of and compliance with the relevant building and fire regulations. Failing to comply with the applicable rules can prevent occupancy, delaying the use of the building and significantly impacting the overall return on investment.
The intent of most building and fire regulations is to establish the minimum requirements for safeguarding public health, safety, and general welfare. The key term here is “minimum.” The following questions come to mind: Do the minimum requirements align with the goals and objectives of your client, and the intended operations of the enterprise? Are you confident the minimum requirements provide the desired level of life safety, property protection, continuity of business operations, or preservation of cultural resources should a fire occur? Has this decision been given proper consideration, and have the goals and objectives been adequately articulated? For instance, building regulations have traditionally addressed property protection only to the extent necessary for occupant and firefighter safety. How might this realization impact the overall implementation of the fire protection strategy during not only the design and construction process, but also throughout the life of the building?
It is worthy to note that while model codes serve as the basis for most building regulations in various jurisdictions across the United States, most jurisdictions and governmental agencies amend the various adopted versions of the model regulations, or enact bylaws that override the rules of the adopted model codes and standards. Thus, a uniform level of safety from fire is not necessarily prescribed nor implemented throughout the United States.
What do building regulations say about fire protection systems?
Building regulations mandate active fire protection systems, largely automatic sprinkler systems, based upon the occupancy types associated with the building, the size and location of the fire area, and the expected occupant load. For instance, the International Building Code (IBC) requires automatic sprinkler systems in Group A-2 occupancies, such as restaurants, where one of the following conditions exists:
- The fire area exceeds 5,000 sq ft.
- The fire area has an occupant load of 100 or more.
- The fire area is located on a floor other than the level of exit discharge.
Similar requirements are found in NFPA 5000: Building Construction and Safety Code and NFPA 101: Life Safety Code. Additionally, model codes require sprinkler systems for certain types of buildings regardless of the occupancy type. For example, sprinkler systems are required for all high-rise buildings.
Building regulations also allow for “alternative automatic fire-extinguishing systems” or “other automatic extinguishing equipment,” but provide limited direction on when such systems are needed or should be considered. Depending upon the model code, these “alternative” or “other” systems are identified as wet chemical, dry chemical, foam, carbon dioxide, halon, clean-agent, water spray, foam-water, and water mist. Reference is normally made to the associated NFPA standards for the system under consideration for relevant design and installation provisions, such as NFPA 2001: Standard for Clean Agent Fire Extinguishing Systems or NFPA 17: Standard for Dry Chemical Extinguishing Systems.
However, when a building or fire regulation references an “alternative” or “other” system, it usually does so in the context of providing life safety for building occupants, usually as an alternative to the requirement for installing an automatic sprinkler system.
Property protection and business continuity
Depending on the facility or operation under consideration, certain fire protection standards do address fire safety beyond life safety and include provisions for property protection and business continuity. However, these standards are not necessarily mandated and referenced by the applicable building and fire regulations. The design engineer needs to be aware of these other standards and how they might impact the overall project and serve to satisfy the overall fire protection goals of the building owner.
An example of such a fire protection standard is NFPA 76: Standard for the Fire Protection of Telecommunications Facilities. The purpose of NFPA 76 is specifically to provide a minimum level of fire protection in telecommunications facilities, to provide a minimum level of life safety for the occupants, to protect the telecommunications equipment, and to preserve service continuity.
The design engineer also needs to be aware of any insurance company input, as these loss control and underwriting recommendations typically serve to address property protection and business continuity concerns. Even so, the agreed-upon level of fire protection for the facility still must be considered and gauged with that of any insurance company recommendations. The degree of property protection recommended by the insurance company is normally based on the policy purchased and the overall philosophy of the insurer, not necessarily the long-term objectives and needs of the building owner.
System design, installation standards
Virtually no comprehensive guidance facilitating the decision as to why one type of system should be chosen over another is available as a regulatory document or generic application guide. Instead, each reference standard tends to provide some commentary about the fire hazards that could be protected against using the given system addressed by the standard. Depending on the specific reference standard and system, certain design and installation provisions could also be provided. For instance, NFPA 12: Standard on Carbon Dioxide Extinguishing Systems includes information about the design of the carbon dioxide systems for a specific hazard once a decision has been made to install a carbon dioxide system for that hazard. Such information can include design concentrations, flooding factors, and volume factors specific to these types of systems.
Some standards relay system application information in other forms. NFPA 2001 provides advisory annex language indicating that clean agent fire extinguishing systems are useful within certain limits for extinguishing fires in specific hazards or equipment, and in occupancies where an electrically nonconductive medium is essential or desirable or where cleanup of other media presents a problem. Such total flooding clean agent systems are used primarily to protect hazards that are enclosed or equipment that in itself includes an enclosure to contain the agent. A list of typical hazards that could be suitable for protection by clean agent systems is provided and includes:
- Electrical and electronic hazards
- Subfloors and other concealed spaces
- Flammable and combustible liquids and gases
- High-value assets
- Telecommunications facilities.
NFPA 2001 also states that clean agent systems could be used for explosion prevention and suppression where flammable materials collect in confined areas.
Other reference standards do not directly identify the hazards they are intended to protect, but rather tie the appropriateness of the system to specific listing and testing requirements. For example, NFPA 750: Standard on Water Mist Fire Protection Systems states that water mist protection systems are to be designed and installed for the specific hazards and protection objectives specified in the listing. The characteristics of the specific application, such as compartment variables and hazard classification, are to be consistent with the listing of the system. Furthermore, an evaluation of the compartment geometry, fire hazard, and system variables must be performed to ensure that the system design and installation are consistent with the system listing.
In turn, NFPA 750 requires the listing of water mist fire protection systems to be based on a comprehensive evaluation designed to include fire test protocols, system components, and the contents of the manufacturer’s design and installation manual. An annex in NFPA 750 includes a list of fire test protocols and the associated listing organizations. It should be obvious that the consulting design engineer needs to be sufficiently familiar with the application and limits of the listing protocols, as well as the design and installation manual for each type of water mist system that might be under consideration.
It is important to recognize that with many of these “alternative” or “other” systems, not just water mist systems, a generic design approach, such as for automatic sprinkler systems as outlined in NFPA 13: Standard for the Installation of Sprinkler Systems, does not exist. Many of these “alternative” systems are of a proprietary nature and the design and installation provisions are specific to the manufacturer of each type of system. For a given hazard, the design, installation, and operational details of one manufacturer’s water mist system are likely to be significantly different from that of another manufacturer. It is worth noting that even with sprinkler systems, more specialized devices are entering the marketplace.
The decision-making process
The consulting engineer needs to possess a thorough knowledge of the limitations and uses of the various types of “alternative” systems he or she might consider as part of the overall fire protection package. It often falls upon the individual consulting engineer to develop his or her own method or application guide for selecting and recommending the most appropriate “alternative” system to meet the overall project objectives. Information from each of the individual reference standards as well as from other sources, such as system manufacturer materials listing protocols and fire tests, is essential in developing such an application guide. Ideally, a comprehensive fire risk assessment should serve as the basis for structuring any application guide or method for recommending a fire protection system. At a minimum, the decision process should be risk-informed.
A fire risk assessment is a process used to characterize the risk associated with fire that addresses the fire scenario or fire scenarios of concern, their probability of occurring, and their potential consequences. Within the context of the risk assessment, fire protection systems serve to mitigate the consequences. In undertaking a fire risk assessment, the level of acceptable fire risk needs to be sufficiently considered and articulated. The fire risk assessment will help crystallize the overall intent and purpose of any fire protection system, and how it fits into the overall fire safety strategy. Preferably, the fire protection systems need to be linked to the overall goals and objectives of not only the building owners, but also other key stakeholders involved with the project.
Certain fire protection standards specifically call out the use of fire risk assessments. For example, NFPA 75: Standard for the Fire Protection of Information Technology (IT) Equipment indicates that a fire risk analysis can be used to determine the construction, fire protection, and fire detection requirements for IT equipment, rooms, and areas. NFPA 75 identifies—among other things that need to be considered to determine the level of acceptable fire risk—factors such as the effect of loss of function of IT equipment on life safety, for example, process controls; threat of burning equipment to occupants and other property; and economic impact from loss of function, records, or physical assets. Numerous resources on fire risk assessments, including several chapters in the SFPE Handbook of Fire Protection Engineering and NFPA 551: Guide for the Evaluation of Fire Risk Assessments, are available to the consulting fire protection engineer in this regard.
Another resource available for structuring the decision making process is NFPA 550: Guide to the Fire Safety Concepts Tree. The “tree” can be used to develop and analyze the potential impact of fire safety strategies, and help identify gaps and areas of redundancy. The logic of the “tree” is directed toward the achievement of specified fire safety objectives that need to be clearly articulated. Strategies for achieving the objectives are divided into two categories: “prevention of fire ignition” and “managing fire impact.” Active fire protection systems can be employed to accomplish both: preventing a fire from starting, for example, inerting the atmosphere once the flammable limits of a particular fuel are sensed; and by managing the impact of the fire once ignition has occurred, for example, suppressing or controlling the fire, or safeguarding the exposed. Additionally, the system can be used to protect the entire building or just specific areas or operations.
Articulating goals, objectives
Ideally, the objectives necessary to achieve the stated goals will be quantified in some manner such as a maximum permitted fire size or concentration of products of combustion. In other words, how big of a fire and for what duration can the owner tolerate and still achieve his or her life safety or property protection goals? From a fire protection engineering perspective, especially through the application of performance-based design approaches, the fire can be quantified in terms of heat release rate as a function of time.
Tolerable fire size and growth rate—factors not explicitly described in building regulations and most design standards—will help inform the decision as to whether extinguishment, suppression, or control of the fire is needed; how soon after ignition system activation must occur; and what quantity of agent will be needed. The type of fuel and its location and orientation, ignition source, and room ventilation greatly influence a fire’s growth and heat release rate.
With respect to the various types of systems that can be used, some systems are more appropriate for fire suppression after a relatively short period of agent discharge followed by a longer time period in which the concentration of agent is held in the vicinity or room of the fire. Other systems are better suited for fire control in which the agent is directly applied to the burning and adjacent surfaces for an extended period of time. For many of these systems, a supplemental detection system is necessary to activate and control the system. Such detection systems and devices need to be integrated into the overall fire safety strategy, and selected and designed so that they initiate fire protection system discharge within the time period necessary to achieve the overall fire safety goals and objectives.
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.