Fire fighting system

a system of equipment used to prevent, extinguish, localize, or block fires in enclosed spaces. Automatic fire-fighting systemsare installed in buildings and rooms where the fire hazard is comparatively high. A distinction is made between systems thatare actuated automatically and operate according to a predetermined program and those that are actuated by an operator;the former are called automatic fire protection systems, the latter fire protection units. An automatic fire-fighting systemincludes a sensor capable of detecting combustion, alarm signaling devices, fire-extinguishing equipment, starting andstopping devices, and feeders for the fire-extinguishing substance; in some cases, it includes control equipment for theproduction process being protected. Atomizers, foam generators, and pipe nozzles form and direct the stream of the fire-extinguishing substance, which may be a liquid, foam, powder, or gas. Fire-extinguishing substances are fed into the systemfrom a centralized supply, such as a water supply, or from self-contained or combined feeders

The most widely used systems employ water (sprinkler and drencher systems), carbon dioxide, aerosols, or powders. Asprinkler system consists of a grid of pipelines located on the ceiling of the room, with sprinkler heads attached to the pipesby threaded connections. The opening of a sprinkler is kept closed by a disk held in a closed position by a thermal lock. If theroom temperature rises to a specified point, the lock is destroyed and the disk opens, admitting water to the room

Drencher systems, which use nozzles without thermal locks, are actuated either by a sprinkler installed in a trigger air line orby a cable-type thermal lock. Automatic fire protection systems are classified according to the time elapsed between the startof the fire and the actuation of the system as ultrahigh-speed (to 0.1 sec), high-speed (to 3 sec), and standard (to 180 sec).The fire-extinguishing substance can be applied for periods ranging from 30 sec to 60 min

A fire fighting system is probably the most important of the building services, as its aim is to protect human life and property, strictly in that order  

It consists of three basic parts

• A large store of water in tanks,either under ground or on top of the bulding called fire storage tanks
• A specialised pumping system
• (A large network of pipes ending in either hydrants or sprinklers ( nearly all buildings require both of these systems

A fire hydrant is a vertical steel pipe with an outlet, close to which two fire hoses are stored (A fire hydrant is called a standpipe in America). During a fire, firefighters will go to the outlet, break open the hoses, attach one to the outlet, and manually open it so that water rushes out of the nozzle of the hose. The quantity and speed of the water is so great that it can knock over the firefighter holding the hose if he is not standing in the correct way.  As soon as the fire fighter opens the hydrant, water will gush out, and sensors will detect a drop in pressure in the system. This drop in pressure will trigger the fire pumps to turn on and start pumping water at a tremendous flowrate

A sprinklers is a nozzle attached to a network of pipes, and installed just below the ceiling of a room. Every sprinkler has a small glass bulb with a liquid in it. This bulb normally blocks the flow of water. In a fire, the liquid in the bulb will become hot. It will then expand, and shatter the glass bulb, removing the obstacle and causing water to spray from the sprinkler. The main difference between a hydrant and a sprinkler is that a sprinkler will come on automatically in a fire. A fire hydrant has to be operated manually by trained firefighters - it cannot be operated by laymen. A sprinkler will usually be activated very quickly in a fire - possibly before the fire station has been informed of the fire - and therefore is very effective at putting out a fire in the early stages, before it grows into a large fire.  For this reason, a sprinkler system is considered very good at putting out fires before they spread and become unmanageable.  According to the NFPA of amrica, hotels with sprinklers suffered 78% less property damage from fire than hotels without in a study in the mid-1980s