Fire sprinklers are a building system used to prevent the spread of fire. They consist of a network of pipes connected to dispensing units known as heads. In the event of a fire, the heads will release water or dry chemicals onto the flames. The requirements for sprinkler systems are fairly standard in commercial structures, but tend to vary in residential applications.
In the U.S., fire sprinkler system requirements are set by the National Fire Protection Agency (NFPA). NFPA publishes standards outlining the different types of systems that may be used, how they should be installed, and the type of equipment and piping that may be included. NFPA Standard 13 covers fire sprinkler requirements, while 13D addresses residential systems and 13R covers multifamily units.
While NFPA Standard 13 provides detailed information on commercial sprinklers, it is important to understand that this standard is not a law in and of itself. The standard only becomes law when it is adapted into state or local building codes. In the vast majority of U.S. cities, NFPA 13 is the legal standard for commercial sprinklers. Each state is permitted to adapt the standard to its own needs, so some changes may be made depending on the region.
Surprisingly, not all commercial buildings are required to have sprinkler systems. This requirement is determined by local codes, and may be based on such factors as the size and layout of the building, the location of exits, and the number of occupants within the structure at any given time. Most local building codes also classify a commercial building based on the risk of fire, which involves activities or materials found inside the structure. When sprinkler systems are required by code, they must be installed and built according to NFPA 13.
Based on successful lobbying by NFPA, the National Fire Sprinkler Association, and the International Residential Sprinkler Association, the International Code Council (ICC) made changes to its standards in 2006. The 2006 ICC building codes were the first to require sprinklers in all new residential structures. After significant protesting by home builders, the ICC decided to reconsider this change for the 2010 to 2012 codes. As of October 2009, no decision had been made, but the result of this debate may affect the 2009 ICC code on sprinkler requirements.
There are several types of sprinkler systems that can be used under NFPA 13, and each is acceptable for both commercial and residential applications. The most common is a wet system, where the pipes are prefilled with water. When the heads are exposed to high heat levels, a fluid-filled bulb on the head will pop and release the water. Dry systems do not fill with water until one of these bulbs has popped. The resulting pressure change in the pipes causes water to enter the system and exit through the sprinkler heads.