Most visibly effective mitigation measure in fire and life safety in buildings is the provision of fire sprinklers. When fire sprinklers are provided is like having, sometimes, hundreds of fire fighters at the ready and around the clock. Each sprinkler is capable to detecting potential fire and automatically activating to suppress the fire. Yet, fires are still occurring every day.
One may wonder why. Indeed, despite continual improvements of design requirements, many fires do overwhelm fire sprinklers. Every fire does present an opportunity to evaluate sprinklers effectiveness. The National Fire Protection Association (NFPA) has been collecting data on fire sprinklers. Statistical data, even though it is far from being perfect, it is still providing lots of useful information on fires and fire sprinklers effectiveness.
Fire Sprinklers: Most Bang for the Money
- Heat detection
- Localized suppression
- Hazards paired to protection
- Hydraulically calculated
- Water flow detected
- Water flow triggers alarm
- Life Safety bonus
- Life safety bonus
Standard Continually Improved
It is hard to believe that the original standard for the installation of fire sprinklers in buildings was only a 25 pages document in 1896. The standard for the installation of fire sprinklers in buildings evolved to become todays standard with over 430 pages documents. In addition to common chapters found in most of the NFPA Standards, NFPA 13 goes into a great effort to classify and describe different fire hazards for the purpose to providing appropriate and sufficient suppression level to be effective at controlling the fire. For each type of fire hazards, the standard prescribes a corresponding design criterium is mandated for effective fire suppression.
The ultimate measure of a design Standard effectiveness is the successful control of fires. Indeed, fire sprinkler systems are designed to control fires in lieu of extinguishment. This may trigger questions as to the difference between fire control and fire extinguishment. Fire sprinklers were always intended to control the fire. That means that once fire sprinklers activate, the fire would be expected to not grow beyond the area of origin. Fire fighters, who are expected to be notified shortly after detection of water flow, extinguish the fire manually.
Fire Sprinklers Limitations
Many limitations of fire sprinklers are reflected in the requirements found in the standard. These, generally, emanate from observed performance of fire sprinklers during full-scale fire tests. These fire tests are critical for evaluating the performance of sprinklers in a realistic setting.
Given that humans are constantly creating new materials with new and often different properties. These properties may end up being more fire challenging. Indeed, despite testing performance of fire sprinklers, we still are surprised once and while when fire sprinklers are overwhelmed by a fire.
For those familiar with fire behavior of different materials may not be surprised. Indeed, we have learned lots about lots of fire behavior of fire behavior of many materials. However, what is often not appreciated is that the combination of different materials may present combined behavior that is more challenging than materials burning alone. Shapes and configuration of fuels in a space play both important roles.
Key Design Decisions
Fire sprinkler designers must make key decisions to properly classify fire hazards, especially when it comes to storage of goods. Not only the nature of the goods is important but also the storage arrangement as well as the height of storage. Cold storage presents a different additional hazard of freezing. Special measures are required by the Standard to address subfreezing temperature while providing fire protection to the facility.
All designers have a great responsibility for pairing hazards and fire protection. NFPA Standards come with explicit requirements but also annexes. Annexes are explanatory language and clarifications of explicit requirements.
It must be stated that generally fire sprinkler systems require a fire pump if the water quality is not enough. Fire pumps are not necessarily required for every sprinkler system. If the required pressure cannot be provided by City water supply system, then a fire pump would be needed. Due to the height of tall buildings, fire pumps are used to provide the pressure to the top levels.
Compounded Challenges: Installations
Given that fire sprinklers performance is critical to control a fire, nearly all fire sprinklers are required to be hydraulically calculated to provide appropriate flows and pressures for every sprinkler. These metrics are of a paramount importance as well as other metrics such as coverage.
These are the simplest metrics to inspect and verify their compliance with NFPA 13. It all involves installation of fire sprinkler systems. Indeed, the design of the fire sprinkler system can be flawless, but its installation is sometimes problematic. It is expected to find deviations from exact requirements found in regulations. It is however expected that the Industry Standard to be met, otherwise deviations may not be acceptable to the Authority Having Jurisdiction (AHJ).
Differences in several fire sprinkler systems are always present. It is the nature of workmanship is ever inconsistent. It should not be surprising if those differences are acceptable per sprinklers regulations and the AHJ.
Another key engineering requirement in the design of fire sprinklers is hanging, bracing, restraint of fire sprinkler systems. This is especially important in earthquake prone regions. The goal of the design is to allow fire sprinkler piping to move independently from the structure. The result would minimize failure of the sprinkler piping.
At times fire sprinkler requirements are more stringent than requirements found in NFPA 13. Indeed, Factory Mutual Global has its own requirements for the design fire sprinklers. This is due to the fact the Factory Mutual Global is known to insure high risk properties. Examples of such properties would be manufacturing facilities, aircrafts hangars, special amusement facilities. As such FM Global has developed their own criteria of pairing hazards and protection.
Climatic Change Consideration
With the undeniable climate changes, we have seen sprinkler system failures due freezing temperatures. Locations where failures occurred were not normally prone to freezing conditions. It is affecting both dry and wet fire sprinkler systems. This will force many building owners to consider mitigating measures. It is equally undeniable that there is will be a financial penalty to upgrade existing fire systems.
Fire sprinklers have revolutionized the use of buildings. Indeed, with fire sprinklers, we build taller and larger. With fire sprinklers, we mitigate known hazards. Fire sprinklers do indeed minimize the loss of life and property. They also reduce business interruptions. This is so if fire sprinklers are appropriately paired with well identified hazards. In addition to appropriate design, fire sprinklers need to be installed per both Industry Standards and design requirements. Then, as for every physical system is appropriate inspections, testing, and maintenance per regulations.