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The U.S. Experience
Sprinklers Effective Elements of Fire Protection in Buildings

Automatic sprinklers are highly effective elements of fire protection in buildings. When sprinklers are present and operative, they are effective 96 percent of the time when the fire was large enough to activate them.

According to the National Fire Protection Administration, sprinklers are designed to confine a fire to the room of origin, or the design fire area, whichever is smaller.

Therefore, the benefits of sprinklers will tend to come in the following scenarios:

• A fire that would otherwise have spread beyond the room of fire origin will be confined to the room of origin, resulting in a smaller fire-damaged area and less property damage;

• A fire that would otherwise have grown larger than the design fire area in a room larger than that area will be confined to the design fire area, resulting in a smaller fire damaged area and less property damage.

• A fire will be confined to an area smaller than the room or the design fire area, even though that degree of success goes beyond the performance assured by the design, resulting in a smaller fire-damaged area and less property damage.

In “U.S. Experience with Sprinklers and Other Automatic Fire Extinguishing Equipment,” published in January by the NFPA Fire Analysis and Research Division, John R. Hall, Jr., says, “For most properties other than homes, the value of sprinklers can be more clearly seen and more appropriately measured by their success in preventing catastrophic multiple-death incidents.”

The NFPA has no record of a fire killing three or more people in a completely sprinklered building where the system was properly operating, except in an explosion or flash fire or where civilians or firefighters were killed while engaged in fire suppression operations.

For decades, this statement – phrased in terms of sprinkler ability to prevent a defined class of severe outcomes – had been NFPA’s principal statistic measuring sprinkler effectiveness.

And because explosions, flash fires, and industrial fire brigades are rarely found outside mercantile and industrial properties and associated storage facilities, the following statement is also true: NFPA has no record of a fire killing more than two people in a completely sprinklered public assembly, educational, institutional, or residential building where the system was properly operating.

The NFPA says, there are certain fire situations where even a complete sprinkler system will have limited impact: (a) Explosions and flash fires that may overpower the system; (b) Fires that begin very close to a person (e.g., clothing ignition) or unusually sensitive and expensive property (e.g., an art gallery) where fatal injury or substantial property loss can occur before sprinklers can react; and (c) Fires that originate in unsprinklered areas (e.g., concealed wall spaces) or adjacent properties (e.g., exposure fires), which may grow to unmanageable size outside the range of the sprinkler system.

These situations can arise when (a) sprinkler standards are based on design fires less severe than explosions or flash fires, as is normally the case; (b) sprinkler objectives are defined in terms of a design fire area larger than the distance implied by a victim intimate with ignition; or (c) sprinkler standards exclude certain potential areas of fire origin from their definition of complete coverage, which is typically but not always the case.

Automatic Extinguishing Equipment Effectiveness

A number of approaches can be and have been used to quantify the effectiveness and value of sprinklers and other automatic extinguishing systems.

These approaches may be grouped into the following three types:

• Qualitative judgments as “effective” or “satisfactory” by fire investigators or others completing incident reports;

• Reduction in life loss per fire or property loss per fire; and

• Reduction in the likelihood of large fire size or severity, such as fire spread beyond room of origin, multiple deaths or large property loss.

For all confined or non-confined fires large enough to activate sprinklers, excluding buildings under construction, sprinklers operated and were effective 91 percent of the time.

Sprinkler systems are so effective that it can be tempting to overstate just how effective they are. For example, some sprinkler proponents have focused too narrowly on the reliability of the components of the sprinkler system itself. If this were the only concern in sprinkler performance, then there would be little reason for concern at all, but human error is a relevant problem.

On the other hand, some people, concerned that sprinklers will be treated as a panacea to the detriment of other essential elements of fire protection, have treated human errors as intrinsic to sprinkler performance.

In fact, all forms of active and passive fire protection tend to show more problems with human error than with intrinsic mechanical or electrical reliability.

For sprinklers that operated, effectiveness was uniformly high in all property classes. Effectiveness was higher for wet pipe sprinklers (97 percent for all structures) than for dry pipe sprinklers (91 percent). Effectiveness was much lower for dry chemical systems (81 percent for all structures) and for foam systems (84 percent for all structures) than for any other automatic extinguishing system analyzed.

When sprinklers operate but are ineffective, the reason usually had to do with an insufficiency of water applied to the fire, either because water did not reach the fire (42 percent of cases of ineffective performance) or because not enough water was released (29 percent). Other leading reasons were inappropriate system for the type of fire (11 percent) lack of maintenance (3 percent), and manual intervention that defeated the system (3 percent). Only 3 percent of cases of sprinkler ineffectiveness were attributed to component damage.

When people die in fires despite the presence of operating sprinklers, it is often because they are close to the fire when it begins, 85 percent of fatal victims in the area of origin and 34 percent with their clothing on fire when sprinklers operate, compared to 53 percent and 7 percent of fatal victims when no automatic extinguishing equipment was present) or because they had some severe vulnerabilities or limitations before fire began (44 percent of fatal victims when sprinklers operated were age 65 or older, and 34 percent returned to fire after escaping, were unable to act, or acted irrationally when fatally injured, compared to 28 percent and 18 percent of fatal victims in general).

It is important for all concerned parties to consider the following:

• Distinguish between human and mechanical problems because they require different strategies;

• Include both as concerns to be addressed when deciding when and how to install, maintain, and rely on sprinklers and other automatic extinguishing systems;

• Strive to use performance analysis in assessing any other element of fire protection; and

• Remember that the different elements of fire protection support and reinforce one another and so must always be designed and considered as a system.

Sprinklers apparently are still rare in many of the places where people are most exposed to fire, including educational properties, offices, most stores, and especially homes, where most fire deaths occur. There is considerable potential for expanded use of sprinklers to reduce the loss of life and property to fire. FSM

Source: “U.S. Experience with Sprinklers and Other Automatic Fire Extinguishing Equipment,” published by the NFPA Fire Analysis and Research Division, January 2009.