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ESFR (Early Suppression Fast Response) sprinkler systems are designed to achieve fire suppression for a specific type of storage occupancy before the fire becomes fully developed. ESFR heads vary with K-factors of 11.2, 14.7, 17 and 25.2 with as well as pressures of 50 and 70 psi. In most cases ESFR systems have not been tested for non-storage occupancies.
Conventional sprinkler systems are designed to control a fire and prewet the surrounding area until it can become extinguished by the fire department or trained fire brigade. The sprinkler heads are smaller than ESFR heads and are designed to discharge lower pressures and flows. Conventional systems offer proper protection for manufacturing hazards such as flammable liquid and aerosol operations, injection molding and occupancies with shielded combustibles.
The main advantage of an ESFR system over a Conventional sprinkler system is the possible elimination of the requirement for in-rack sprinklers in rack storage areas. However if suppression mode sprinklers are obstructed or are not designed properly they will fail to suppress a fire and the results can be devastating. Specific detail to sprinkler design and installation is most important. The best ESFR guideline is Property Loss Prevention Data Sheet 2-2 "INSTALLATION RULES FOR SUPPRESSION MODE AUTOMATIC SPRINKLERS," which is published by FM Global and is available for free on their web site at www.fmglobal.com. The data sheet states there are a total of six known fires involving suppression mode sprinkler protection. In all of these incidents, suppression mode protection was successful and no more than four sprinklers operated. In the two incidents for which detailed information was available, the sprinklers involved were not obstructed.
It is critical that exact guidelines from Fata Sheet 2-2 regarding obstructions are followed. Some of the key problems found today in most ESFR systems are that:
- All ESFR sprinkler heads should be located a minimum of 12 in. horizontally from the edge of the bottom chord of open web joists and trusses.
- All ESFR sprinkler heads should be located a minimum of 12 in. horizontally from the edge of all light fixtures located below the sprinklers.
It is critical to provide adequate clearance from obstructions below ESFR sprinklers in order for ESFR sprinkler systems to work properly. One or two obstructed heads over a fire area could lead to an uncontrolled fire.
Another common problem found is that 1 hour fire rated partitions are recommended between areas protected by ESFR and conventional sprinklers.