NFPA Journal®, November/December 2009

Anniversaries provide a special opportunity to look back at milestones in the development and recognition of automatic sprinklers. It was 10 years ago, in 1999, that the Federal Emergency Management Agency recommissioned America Burning, leading to the publication of an updated report on the fire problem in the United States. One of the principal findings was this: "The most effective fire loss prevention and reduction measure with respect to both life and property is the installation and maintenance of fire sprinklers."

Fifteen years ago, in 1994, the U. S. General Services Administration (GSA) addressed the issue of how effective sprinklers are, under an obligation imposed by the Federal Fire Safety Act of 1992. After studying the issue, the GSA determined that an automatic sprinkler system could provide life safety from fires by preventing flames from leaving the room of origin, limiting the fire size to no more than 1 megawatt, and preventing flashover in the room of fire origin.

Preventing flames from leaving the room of origin ensures that the fire does not continue to grow and spread. Limiting the size of the fire to no more than 1 megawatt ensures that the total impact of the fire will be manageable. Without sprinklers, a fire in even a single upholstered chair can grow to 2 megawatts, while a sofa fire can reach 4 megawatts. Fires in small rooms can quickly grow to flashover, when heated gases at the ceiling ignite all combustible items in an enclosure simultaneously. Preventing flashover in the room of fire origin limits the production of toxic gases that can spread to adjacent areas even in cases where the fire itself is contained.

Even the 1-megawatt fire is a maximum based on conservative assumptions relative to ceiling height and sprinkler response. In typical rooms, sprinklers are expected to respond when then fire is considerably smaller, on the order of a tenth to a quarter of a megawatt, or the range from a small to large wastebasket fire. This is because of the significant technological advancement that took place 30 years ago: the development of a new generation of fast-response sprinklers.

The Los Angeles residential sprinkler test series, in which fast-response prototype residential sprinklers were field-tested for the first time, took place in the summer and fall of 1979, and included 60 full-scale fire tests that demonstrated the ability of the new sprinklers to provide life safety even in small residential compartments.

The residential sprinklers were the first in the family of fast-response sprinklers, a family that grew to include ESFR (early suppression fast response) sprinklers for storage applications, as well as QR (quick response) and QREC (quick response extended coverage) sprinklers for light and ordinary hazard applications. These sprinklers all employ fusible links or bulbs that are more thermally sensitive than those of traditional sprinklers, allowing them to react faster to the heat of a fire. This is done by reducing mass in the sensing element, using a thinner link or smaller-diameter bulb, while maintaining the strength of the sprinkler assembly needed to hold back the water pressure in the absence of a fire. Faster sprinkler response leads to more rapid control of the fire, which means that, in many cases, only one or two sprinklers closest to the fire will need to operate to provide control or suppression.

Today, NFPA’s sprinkler system installation standards mandate the use of these fast-response sprinklers in almost all areas in which people live, work, and play. On the 30th anniversary of the Los Angeles residential fire tests, the level of protection fire sprinklers provide is higher than ever.

Russ Fleming, P.E., is the executive vice-president of the National Fire Sprinkler Assocaition and a member of the NFPA Technical Correlating Committee on Automatic Sprinklers.