The measures to mitigate or lessen fire hazards are normally called “fire protection measures.” The National Fire Protection Association standards and local building fire codes set the standards for application and design of fire protection. The types of measures can be broken down as follows:
- Life safety
- Passive fire protection
- Active fire protection
- Manual fire protection
Life Safety
Life safety measures generally include the fire protection measures required under the building, fire, or life safety codes. The main objective of these codes is to ensure that:
- The occupants can leave the station without being subject to hazardous or untenable conditions (thermal exposure, carbon monoxide, carbon dioxide, soot, and other gases).
- Firefighters are safely able to effect a rescue and prevent the spread of fire.
- Building collapse does not endanger people (including firefighters) who are likely to be in or near the building.
- To meet these objectives, fire safety systems provide the following performance elements:
- Detect a fire at its earliest stage.
- Signal the building occupants and/or the fire department of a fire.
- Provide adequate illumination to an exit.
- Provide illuminated exit signs.
- Provide fire-separated exits within reasonable travel distances from all areas of a building. These exits shall terminate at the exterior of the building.
- Provide fire separations between building floors and high-hazard rooms to prevent the spread of fire.
- Provide passive protection to structural components to prevent their failure due to fire exposure.
Passive Fire Protection
Passive measures are static measures that are designed to control the spread of fire and withstand the effects of fire. These measures are the most frequently used methods of protecting life and property in buildings from a fire. This protection confines a fire to a limited area or ensures that the structure remains sound for a designated period of fire exposure. Its popularity is based on the reliability of this type of protection, since it does not require human intervention or equipment operation. Common types of passive protection include fire-stopping, fire separations, equipment spacing, use of noncombustible construction materials, use of low-flame-spread/low-smoke-development rated materials, substation grading, provision of crushed rock around oil-filled equipment, etc.
The degree of passive protection for a building structure would be based on the occupancy of the area and the required structural integrity. The structural integrity of a building is critical in order to preserve life and property. The premature structural failure of a building before the occupants can evacuate or the fire department can suppress the fire is a major concern. Building and electrical codes will provide some of the criteria for structural fire resistance.
IEEE 979 includes recommendations on these measures relative to substation design.
Active Fire Protection
Active fire protection measures are automatic fire protection measures that warn occupants of the existence of fire and extinguish or control the fire. These measures are designed to automatically extinguish or control a fire at the earliest stage without risking life or sacrificing property. The benefits of these systems have been universally identified and accepted by building and insurance authorities. Insurance companies have found significant reductions in losses when automatic suppression systems have been installed.
An automatic suppression system consists of an extinguishing agent supply, control valves, a delivery system, and fire detection and control equipment. The agent supply may be virtually unlimited (such as with a city water supply for a sprinkler system) or of limited quantity (such as with a water tank supply for a sprinkler system). Typical examples of agent control valves are deluge valves, sprinkler valves, and halon control valves. The agent delivery systems are a configuration of piping, nozzles, or generators that apply the agent in a suitable form and quantity to the hazard area (e.g., sprinkler piping and heads). Fire detection and control equipment can be either mechanical or electrical in operation. These systems can incorporate a fire detection means such as sprinkler heads, or they can use a separate fire detection system as part of their operation. These active fire protection systems detect a fire condition, signal its occurrence, and activate the delivery system. Active systems include wet, dry, and pre-action sprinklers, deluge systems, foam systems, and gaseous systems.
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