Understanding Fire System Design: Control
September 13, 2012
Good fire protection relies on three very straightforward goals: first, to contain the fire; second, to extinguish or actively control the fire; and, third, to protect assets. All fire-related regulations try to accomplish these goals. Let's look at the second of those three a little more closely: control the fire.
Codes frequently require built-in means to control, suppress or extinguish fires. Rather than passive systems that resist the effects of fire, these work to defeat it. Originally, extinguishing systems included hydrants and standpipes to assist manual efforts. Extinguishing systems usually now respond automatically.
Although a manual system, standpipes can be an important part of the building's protection system. Standpipes can be wet or dry piping systems that serve as a remote fire hydrant, providing a means for the fire department to supply hose lines in the fire area. Standpipe systems are usually found in buildings of three or more stories or buildings with large floor areas. Standpipes allow fire fighters to avoid long hose runs that are heavy, cumbersome and time-consuming to lay and maneuver.
The most significant fire suppression system is the automatic sprinkler. Its prime purpose is to control or extinguish the fire. Sprinklers were first used to provide property protection based on insurance requirements. Now they are relied upon heavily as a significant component of the life safety system.
Often, codes use sprinklers to reduce or eliminate fire barrier requirements or allow for increases in the base areas and heights allowed for a specific occupancy and construction type. Sprinklers control fire risk much like a high degree of physical containment does.
Building codes identify requirements for sprinkler systems and standpipe systems; details of installation and system design are normally governed by standards such as NFPA 13 "Automatic Sprinkler Systems." In an office building, for example, code may require a sprinkler system based on the size and construction type of the building.
Calculations are required to show that the water supply and pipe sizes are adequate to deliver the water. Either the public water supply or a fire pump must be provided to supply the water pressure, or a separate water supply and pumping system must be provided. Many specialized buildings require higher pressures to meet design criteria. This often mandates that a fire pump be provided to boost the water pressure.
Other extinguishing systems, such as gaseous systems, are primarily for specialized hazards and tend to be aimed at protecting physical assets. These receive little credit in the building code but may be required by either a user or tenant, or be appropriate because of the special nature of the hazard. The most common examples are systems that protect server rooms or generator compartments.
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