Designing passive and active fire protection systems
- Understand active and passive fire protection systems along with select requirements from the International Building Code.
- Learn important considerations when selecting and designing fire protection systems.
The design of fire protection systems should be project-specific, cohesive, and consider the building lifecycle from the design to construction and operation. Passive fire protection systems include structural fire resistance, compartmentation (fire-rated walls, floors), and protection of the openings through them (fire doors, fire dampers, firestop systems). Active fire protection systems include sprinkler systems, alternative automatic fire-extinguishing systems, standpipe systems, fire extinguishers, fire alarm and detection systems, emergency alarm systems, and smoke control systems.
Fire protection systems must meet the client’s goals. At a minimum, buildings must be code-compliant, but owners and developers will consider construction and operational costs, the construction schedule, quality, design excellence, property protection, business continuity, and sustainability goals when seeking out design solutions. Projects often have various end users including customers, tenants, staff, user groups, maintenance, and facilities teams who influence these factors.
Fire protection systems must be cohesive. The best-designed buildings have a fire strategy that guides the selection of passive and active fire protection measures in response to the particular hazards and objectives of that project. Each system must be designed to meet the client’s goals, the fire strategy, and the applicable codes. Fire protection systems have interdependencies with each other and with non-life safety systems. The design team must identify and understand these interdependencies and ensure that they are properly coordinated.
The design phase is just the beginning of the building lifecycle. Fire protection systems must be designed with the construction and operational phases of the building in mind. Constructibility, field conditions, and construction phasing are just a few of the items to consider before and during construction. Post-construction, the owner must then understand and meet their responsibilities for operating, inspecting, testing, and maintaining these systems over the life of the building.
Passive fire protection
Active fire protection
• Fire-resistant-rated construction (walls, floor/ceiling, roof, barrier, partition)
• Fire-resistance rating of structural members
• Fire-resistant joint systems
• Penetration firestopping
• Opening protectives (fire door or window assembly, fire shutter, fire-rated glazing)
• Duct and air transfer openings (combination fire/smoke damper, fire damper, smoke damper).
• Automatic sprinkler systems
• Alternative automatic fire-extinguishing systems
• Standpipe systems
• Portable fire extinguishers
• Fire alarm and detection systems
• Emergency alarm systems
• Smoke control systems.
Table 1: The elements of passive and active fire protection systems. Courtesy: Arup
Design professionals might assume that the construction cost is the top priority for their clients. In reality, clients typically have a range of goals and priorities.
Fire/life safety goals will include life safety, property protection, and business continuity. The importance of the latter two goals will depend on the project type and client. Property protection is critically important in a museum storage facility or a distribution facility. Business continuity is paramount in an air traffic control tower, a trading floor, or a data center. (See Figure 1)
Design excellence and quality are important for many clients. Clients increasingly want to enhance occupant well-being and comfort. This often happens with reduced compartmentation, increased openness, and interconnections between floors. The model building codes facilitate this through non-separated mixed use, access-stair/escalator-floor opening allowances, and atrium provisions. Traditionally considered passive systems, hold-open fire doors and specialty doors, such as fire shutters, with or without egress also may aid in these goals. Unlike truly passive systems, such as walls, these systems are interdependent on other systems including the fire alarm system.
Designing high-performance buildings to meet environmental goals is becoming the norm because of client-led sustainability programs, construction codes, or government-led climate change initiatives. Fire protection engineers can make smart decisions in the design and specification of fire/life safety systems to facilitate sustainability goals. For instance, a structural system using mass timber has a lower carbon footprint than steel, concrete, or masonry and can be sized to provide fire resistance without applied fireproofing or being encapsulated in gypsum.
The building envelope is a major area of focus in high- performance buildings that must also meet requirements for fire safety, such as combustibility, flame-spread performance, and floor-to-floor compartmentation. When selecting a clean agent system, NFPA 2001: Standard on Clean Agent Fire Extinguishing Systems requires consideration of the effects of the agent on the environment including its ozone-depletion potential (ODP) and global warming potential (GWP) as well as how well the agent minimizes the environmental effects of the fire itself. NFPA 2001 publishes the ODP and GWP values for each agent, allowing engineers to evaluate each product.
Construction cost is only one aspect of the lifecycle building cost. Active and passive fire protection systems have operational costs related to inspections, testing, and maintenance that must be considered. Ease of maintenance is also a consideration including equipment required and business interruption, such as the type of smoke/heat detection selected for a high-ceiling space. A question that should be asked is “What are the operational preferences and capabilities of the facilities and maintenance staff?” These are important considerations when selecting fire protection systems.
Reducing the construction schedule is often a high priority and ought to be considered when selecting fire protection systems. A simple example is the use of drop-in or preformed firestop systems as compared with field-applied firestopping. Using a gypsum or mineral fiberboard product for fireproofing may be more labor-intensive when compared with spray-applied fire-resistive material but can eliminate a wet trade, which can be advantageous in certain projects. Prefabricated modular construction is one area where it is critical to consider these trade-offs between the material cost, labor cost, and schedule.
Understanding code requirements
While considering client goals is important, code compliance is required on all projects so the project team must understand the requirements. The International Building Code (IBC) is the model code adopted in most jurisdictions in the U.S. and will form the basis of this overview.
Passive fire protection systems are mostly covered in Chapters 5, 6, and 7 of the IBC. The type of construction required is determined using the height/story/area tables in Chapter 5 for the proposed use groups as defined in Chapter 3. The structural materials (steel, concrete, masonry, heavy timber, metal/wood stud) considered by the project team will also factor into which construction type is selected when more than one type is permitted. For example, a building that is taller than 420 ft must be Type I-A noncombustible construction (3-hour columns, 2-hour floors, beams, bearing walls). However, a 5-story building has multiple options for construction type. The type selected will depend on the client goals outlined previously herein. Fully sprinklered buildings are permitted increased height and floor area over nonsprinklered buildings. This is an example of the trade-offs in the building code between active and passive systems.
The fire-resistance ratings of structural members for each construction type are outlined in Chapter 6. The IBC details various compliance methods for determining the fire resistance ratings in Chapter 7. The most common methods use previously tested fire-resistance rating designs such as in the UL Fire Resistance Directory or Intertek Certification Directory, prescriptive designs per IBC, Section 721, or calculated designs per IBC, Section 722. In the absence of existing tested systems appropriate to the project, the client may elect to have fire testing completed for their project-specific assemblies. The IBC also permits engineering analysis and alternative protection methods.
Separated and non-separated mixed-use approaches, incidental use, and accessory use can be explored in Chapter 5 to determine the compliance strategy for compartmentation. If the building is mixed-use, a non-separated-use approach reduces the number of walls requiring opening protectives and firestopping but may result in a higher construction type depending on the building size and use.
Chapter 5 provides required fire-resistance ratings for separated occupancies. Chapter 7 provides the detailed requirements for fire-resistant-rated construction (fire walls, fire/smoke barriers, fire/smoke partitions, and floors). Fire-resistant joint systems, penetration firestopping, opening protectives (fire door or window assembly, fire shutter, fire-rated glazing), and duct and air-transfer openings (combination fire/smoke damper, fire damper, smoke damper) are all covered in Chapter 7.
Unlike passive fire protection systems, active fire protection requires some form of action/response in order to achieve the life safety objective of detecting a fire, notifying the occupants/fire department, managing smoke, or controlling/suppressing the fire.
Chapter 9 of the IBC outlines requirements for automatic sprinkler systems, alternative automatic fire-extinguishing systems, standpipe systems, portable fire extinguishers, fire alarm and detection systems, emergency alarm systems, and smoke control systems as well as identifies where each system is required. Generally, the requirements of Chapter 9 are based on occupancy. However, specific building areas, hazards, and applications that require protection regardless of occupancy are also outlined. In most instances, the IBC and International Fire Code reference NFPA standards for design, installation, inspection, testing, and maintenance requirements of the active fire protection systems.
The IBC sets forth the minimum requirements, yet providing the code-minimum level of protection may not achieve all project goals. The design team and project stakeholders should consider the project goals to ensure that the fire protection systems are tailored to the project. Designers also should consider the requirements of the local authority having jurisdiction (AHJ), the client, and the insurer that may require fire protection systems exceeding the construction codes.
Throughout the IBC, numerous trade-offs are recognized by using active fire protection systems. In addition to the trade-off previously noted, another example of this is smoke-protected seating, defined by the IBC as, “seating served by means of egress that is not subject to smoke accumulation within or under a structure.” For smoke-protected seating, either a smoke control system complying with Section 909 of the IBC or natural ventilation meeting the performance criteria of the code is provided, and the trade-offs include:
Areas of refuge are not required (Section 1009.3).
- Areas of refuge are not required (Section 1009.3).
- Reduced aisle widths (Section 1029.6).
- Extended travel distances and common paths of travel (Section 1029.7 and 1029.8).
- Longer dead-end aisles (Section 1029.9.5).
- Increased row-length limits for aisle accessways (Section 1029.12.2).
Note that the above is not a comprehensive review of the smoke-protected seating requirements; however, it identifies select requirements of Section 1029 of the IBC as related to trade-offs for providing active fire protection.
Performance-based design can be an integral part of the overall fire strategy for a building, particularly where prescriptive design may not allow the client goals to be fully realized. The IBC allows for performance-based design in a variety of ways including the administrative provision in Section 104.11.
The structural fire-resistance rating can be determined by engineering analysis that compares a proposed design with a previously tested design per Section 703.3, or by advanced modeling methods per Section 104.11 of the IBC.
Engineering judgments are often required for fire-rated assemblies, penetration firestop systems, and fire-resistant joint systems, particularly to address unique design/field conditions that vary from tested systems but can be demonstrated to meet the performance requirements.
In older existing buildings, there may be limited—if any—documentation verifying that the passive fireproofing systems meet applicable fire-resistance ratings. In these cases, the fire protection engineer may need to refer to fireproofing-material resources to determine the likely fire rating, such as the International Existing Building Code.
For active systems, performance-based design also is an integral part of the design process.
Smoke control systems are designed using a rational analysis by a registered design professional per Chapter 909 of the IBC and NFPA 92: Standard for Smoke Control Systems. This may include calculations, computational modeling, or real-world testing.
Audibility and intelligibility of fire alarm audible-notification appliances including public address systems can be modeled to verify and optimize performance. The project team must have relevant fire protection and acoustic expertise to complete these simulations accurately.
Total architecture—the integrated approach
“Total architecture,” was conceived by Sir Ove Arup almost 50 years ago where “all relevant design decisions have been considered together and have been integrated into a whole by a well-organized team." Today, this is more commonly known as integrated design and at its best, includes the design team, contractor, owner, end users, and other stakeholders working towards a common set of goals.
One aspect of the integrated approach is coordination among members of the team and stakeholders. The design team should engage the owner and respective end users early on in the process to inform design decisions. Understanding the client goals and project brief is critical for a project to be successful. It is important to recognize any changes that may impact the design as it progresses. Many times, end users may not be part of the design process, which can present challenges in meeting project goals when seeking beneficial occupancy. Regardless of the passive and active fire protection schemes, considerations that should be addressed in the design process may include:
- Does meeting the minimum requirements of the building and fire codes achieve all project goals/objectives?
- Who are key stakeholders from the client team? Does this include end-user groups?
- Are existing capabilities of the end user sufficient to inspect, test, maintain, and operate new passive and active fire protection schemes being designed? If not, are they accepting of the design schemes involving “new and unfamiliar” systems?
- Is the design too complex? Can it be simplified while still effectively achieving fire protection goals? Is there a risk of complex/difficult usability that may ultimately compromise the designed fire protection?
- Will fire protection schemes be capable of operating throughout the life of the structure?
- Are the schemes and respective changes disseminated throughout the entire team?
Another aspect of total architecture is harmonization of the various passive and active fire protection systems to achieve the integrated fire protection strategy. Numerous systems and elements must be coordinated to align with the fire strategy. These elements include:
- Electrical systems
- Fire suppression systems
- Information technology and communications
- Life safety and means of egress systems
- Mechanical systems
- Security systems
- Fire alarm and emergency communication systems
- Smoke control and management systems
- Building infrastructure
- Fire-resistant rated construction.
Some key considerations include confirming the relationship/coordination between the following items:
- Architectural layout with smoke control, fire suppression, and fire alarm layouts.
- Electrical loads of the above systems with electrical design.
- Alignment of smoke control, suppression, and fire alarm system zones.
- Access control with means of egress.
- Fire-rated construction with opening protectives including fire/smoke dampers.
- Fire alarm with mechanical, elevator, suppression systems, emergency generator, and other fire safety interfaces.
- Evacuation strategy with smoke control and fire alarm.
- Fire protection strategy with emergency action and response plans.
- Division of scope between disciplines and contracts.
- Equipment location with regards to other building systems in terms of meeting required clearances and accessibility for future inspection, testing, and maintenance.
While the above list is not a comprehensive summary, it identifies select items that demonstrate a cohesive design approach to passive and active fire protection systems. Existing buildings present additional unique challenges that are not discussed here.
Following approval by the AHJ and award of construction contract(s), the robust construction-administration process commences. The integrated approach should continue through construction as the team grows and additional stakeholders provide input. Post-award changes need to be coordinated throughout the team in the same manner as they are during design. They also must be evaluated to confirm the fire strategy and client goals are still met. Furthermore, geographic boundaries and the fact that the team may be comprised of multiple design and construction firms must not preclude the coordination and evaluation of the fire protection strategy.
As construction progresses, various codes and standards require acceptance testing of the passive and active fire protection systems. Chapter 17 of the IBC requires special inspections of smoke control systems, sprayed fire-resistance materials, mastic and intumescent fire-resistant coatings, and fire-resistant penetrations and joints. Various NFPA installation codes and standards also require inspection and testing of fire protection systems. Examples of documents that contain requirements for acceptance testing include:
- NFPA 13: Standard for Installation of Sprinkler Systems.
- NFPA 20: Standard for Installation of Stationary Pumps for Fire Protection.
- NFPA 72: National Fire Alarm and Signaling Code.
- NFPA 90A: Standard for the Installation of Air-Conditioning and Ventilating Systems.
- NFPA 2001: Standard on Clean Agent Fire Extinguishing Systems.
Design teams also can refer to NFPA 3: Standard for Commissioning of Fire Protection and Life Safety Systems and NFPA 4: Standard for Integrated Fire Protection and Life Safety System Testing, which offer additional guidance related to integrated fire protection and life safety systems.
Post-construction—operating the building
Operating the building and its fire protection systems must be considered during the design process. As previously discussed, involving the end users in the design process becomes increasingly important as the building is prepared for handover. Two aspects of this preparation include training and documentation.
The extent of training required on the new passive and active fire protection systems will vary from project to project, depending on the complexity of systems and familiarity of end users/maintainers with the new products/technologies. The cost and willingness of the end user/maintenance team to train on using the new fire protection systems should be discussed during design. Long before post-construction operation, the end users should be aware of the requirements, roles, and responsibilities for long-term operations, inspection, testing, and maintenance of the new fire protection systems. The scheduling and scope of training must consider the operational readiness of the systems and end users/maintainers for the specific project. New standard operating procedures and guidelines should be implemented, or existing ones revised as needed, to accommodate the new fire protection systems.
Documentation of the fire protection systems is also an important tool for end users. Complete and accurate operation and maintenance manuals as well as as-built drawings for all fire protection systems are essential for maintaining operations over the system’s life expectancy. The fire and life safety strategy encompassing all systems also should be outlined in this documentation to confirm future system upgrades and/or building modifications and maintain the performance set forth in the original design.
One size does not fit all when it comes to using passive or active fire protection systems. The fire protection and life safety systems for each project should be based on the client’s goals and specific fire hazards for that building. A fire strategy will help align fire protection system selection with the client’s goals.
Fire protection systems have myriad interdependencies between them and other non-life safety systems. The design team must understand them and ensure they are coordinated across the contract documents. The contractor must install these systems correctly and in conformance with the contract drawings and specifications.
Design and construction represent a small percentage of the building lifecycle. Post-construction, the owner must perform their responsibilities for inspection, testing, and maintenance.
Robert F. Accosta Jr. is a senior fire engineer with Arup. He serves as an alternate member of the NFPA 72 Technical Committee on Notification Appliances for Fire Alarm and Signaling Systems.
John Barrot is an associate principal with Arup. He leads the fire/life safety practice in New York.