Fire Suppression

Firefighters have said: "The first five minutes of a fire are more important than the next five hours." Thus fire suppression systems must ensure prompt discovery of incipient fires, quick notification to occupants and firefighters, ready control everywhere in the building, and safe evacuation of occupants. The best systems usually cost more, but they often result in lower building insurance premiums that return the extra outlay in a few years. Comprehensive design includes:

Identifying the hazards. Every occupancy should be examined for every potential source of fire: this includes obvious sources such as hot spots and open flames as well as appliances, light fixtures, radiant heating, smoking, sparks, static, frictional heat, sources of spontaneous combustion, lightning, etc. Then consider the materials around each source: those that burn, those that support combustion, those that produce toxic gases, and the surface area and thickness of each. Ifflammable liquids are involved, find the specific gravity of each. From these investigations an

• Alvin Vener, "Smoke and Fire control"; Engineered Systems magazine (Business accurate map of an area's fire hazard areas can be drawn.

Determining appropriate response. This involves conceptualizing layouts (firefighter access, siamese connections, vertical reach of firetruck ladders, etc.) in consideration of possible fire hazards and nature of the architecture. Some fire eruption scenarios may require tight enclosure while others need much ventilation, and some equipment may require specific response controls: e.g. some electrical equipment requires that its power be shut off before its fire-suppression agent activates.

Designing the system. This includes planning the installation and activation of all system components and controls as well as determining the amount of storage, chase, and access space required for each. In varying interior environments and especially where different machinery is present, optimal methods may differ fundamentally in small areas: e.g. one area may require an effective water-spray delivery pattern while an area only a few yards away can be protected only by a foam. Thus flexibility is often vitally important. One way to promote this is to design small-scale fire-suppression systems that can be as easily moved as the operations they serve. System design also includes such architectural considerations as enabling occupants and firefighters to reach extinguishers and hose racks, installing eyebrows over atriums and open spaces, fitting facades with fire-resistive spandrels, and interrupting shafts and risers every fifth floor.

Protecting the occupants. This includes determining the maximum number of occupants in a space, compartmentalizing each floor into at least two zones separated by a 2 hrfire barrier, designing exit routes, and providing the number of exits required.

Protecting the building. This includes providing dikes and drains for water applications, recovery depressions for certain gases, cleanabil-ity of areas afterward, and the like.

Common fire suppression systems are described briefly below. Before using this section you may want to read Sec. 5.C.5.b. Fire Signal Wiring, and Volume 1, Sec. 8.K. Fire Protection.

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