Fire Fighting article from Encarta '99
Fire-Fighting, techniques used to extinguish fires and limit the damage caused by them. Fire-fighting consists of removing one or more of the three elements essential to combustion—fuel, heat, and oxygen—or of interrupting the combustion chain reaction.
Fire Departments
The Roman emperor Augustus is credited with instituting a corps of fire-fighting vigiles ("watchmen") in 24 BC. Regulations for checking and preventing fires were developed. In the pre-industrial era most cities had watchmen who sounded an alarm at signs of fire. The principal piece of fire-fighting equipment in ancient Rome and into early modern times was the bucket, passed from hand to hand to deliver water to the fire. Another important fire-fighting tool was the axe, used to remove the fuel and prevent the spread of fire as well as to make openings that would allow heat and smoke to escape a burning building. In major conflagrations long hooks with ropes were used to pull down buildings in the path of an approaching fire to create firebreaks. When explosives were available, they would be used for this same purpose. Following the Great Fire of London in 1666, fire brigades were formed by insurance companies. The government was not involved until 1865, when these brigades became London's Metropolitan Fire Brigade. The first modern standards for the operation of a fire department were not established until 1830, in Edinburgh, Scotland. These standards set out, for the first time, what was expected of a good fire department.
Fire-fighting is largely a matter of local jurisdiction in the United States, but many countries have more centralized fire departments. Italy has a national fire service (Corpo Nazionale-Vigili del Fuoco) organized into 92 provinces, administered from 12 regional centres. In Great Britain, local fire departments are organized into county, borough, and special district departments, all under a chief inspector of fire services. In France, fire protection is administered in sectors, except in Paris, where the fire department is operated by the Sapeurs-Pompiers, a brigade of the French army, and in Marseille, where it is administered by the navy. The Japanese government administers 43 regional and 3 metropolitan fire departments. In Denmark, local governments contract for fire-fighting services with companies under supervision of the Ministry of Justice. In Germany, professional fire brigades operate in large cities; volunteer brigades serve the small towns.
In all industrial countries fire fighters undergo training, beginning with probationary fire fighters' school and continuing throughout a fire fighter's career. Great Britain has several fire training centres. In Russia, fire schools are in Moscow and St Petersburg; Sweden and Denmark have similar schools. In some European countries fire protection and fire-fighting are among the courses included in teaching safety engineering.
International fire service and fire protection associations bring together leaders of the fire services of many nations. In Europe, the Comité Technique International de Prevention et d'Extinction du Feu (CTIF) has over 30 member nations, including Russia. The Organización Iberoamericana de Protección Contra Incendios (OPCI) brings together the fire service leaders of all Latin American countries. The Asia-Pacific region is served by the Asian Pacific Fire Safety Association (APAC).
Fighting the Fire
Most fire-fighting consists of applying water to the burning material, cooling it to the point at which combustion is no longer self-sustaining. Fires involving flammable liquids, certain chemicals, and combustible metals often require special extinguishing agents and techniques. With some fuels the use of water may actually be dangerous.
Fire Engines
The first fire engines, which appeared in the 17th century, were simply tubs carried on runners, long poles, or wheels; water was still supplied to the fire site by bucket brigade. The tub functioned as a reservoir and sometimes housed a hand-operated pump that forced water through a pipe or nozzle to waiting buckets. The invention of a hand-stitched leather hosepipe in the Netherlands about 1672 enabled fire fighters to work closer to the fire without endangering their engines and to increase the accuracy of water placement. At about the same time the development of pumping devices made it possible to draw water from rivers and ponds.
In the early 19th century copper rivets replaced the stitching on hoses, and 15 metre (50 feet) lengths coupled with brass fittings enabled fire fighters to convey water through narrow passages, up stairways, and into buildings, while the pumps operated in the street. A cotton-covered rubber hose was developed around 1870. The steam-pump fire engine, introduced in London in 1829 by John Ericsson and John Braithwaite, was used in many large cities by the 1850s. Most steam pumpers were equipped with reciprocating piston pumps, although a few rotary pumps were used. Some were self-propelled, but most used horses for propulsion, conserving steam pressure for the pump.
With the development of the internal-combustion engine early in the 20th century, pumpers became motorized. Because of problems in adapting geared rotary petrol engines to pumps, the first petrol-powered fire engines had two motors, one to drive the pump and the other to propel the vehicle. The first pumper using a single engine for pumping and propulsion was manufactured in the United States in 1907. By 1925 the steam pumper had been completely replaced by motorized pumpers. The pumps were originally of the piston or reciprocating type, but these were gradually replaced by rotary pumps and finally by centrifugal pumps, used by most modern pumpers.
At the same time, the pumper acquired its main characteristics: a powerful pump that can supply water in a large range of volumes and pressures; several thousand feet of fire hose, with short lengths of large-diameter hose for attachment to hydrants; and a water tank for the initial attack on a fire while fire fighters connect the pump to hydrants, and for areas where no water supply is available. In rural areas, pumpers carry suction hose to draw water from rivers and ponds.
Fireboats
Shipboard fires present special problems ranging from small fires in cabin cruisers to tanker fires involving thousands of tonnes of oil. Some of the special problems include complicated ship layouts, the danger of capsizing, and the difficulty of pinpointing and gaining access to the source of the fire. Fireboats, in sizes ranging from small, high-speed, jet-propelled rescue craft to large fire tugs, carry substantially all the fire-fighting equipment found on land apparatus. These include pumps, ladders, and rescue equipment, as well as special equipment necessary for marine fire-fighting and water rescues, including rotating and angled nozzles, portable pumps, floating booms, foam-making apparatus, and special extinguishers such as carbon dioxide systems.
Types of Nozzles
Various nozzles are capable of projecting solid, heavy streams of water, curtains of spray, or fog. Fire trucks carry a selection of nozzles, which are used according to the amount of heat that must be absorbed. Nozzles can apply water in the form of streams, spray, or fog at rates of flow between 57 litres (15 gal) to more than 380 litres (more than 100 gal) per minute. Straight streams of water have greater reach and penetration, but fog absorbs heat more quickly because the water droplets present a greater surface area and distribute the water more widely. Fog nozzles may be used to disperse vapours from flammable liquids, although foam is generally used to extinguish fires in flammable liquids.
Water Additives
A variety of chemicals may be added to water to improve its ability to extinguish fires. Wetting agents added to water can reduce its surface tension. This makes the water more penetrating and facilitates the formation of small drops necessary for rapid heat absorption. By adding foam-producing chemicals and liquids to water, a fire-blanketing foam is produced. Foam is used to extinguish fires in combustible liquids, such as oil, petroleum, and tar, and for fighting fires at airports, refineries, and petroleum distribution facilities.
A chemical additive can expand the volume of foam 1,000 times. This high-expansion foam-water solution is useful in fighting fires in basements and other difficult-to-reach areas because the fire can be smothered quickly with relatively little water damage.
Salvage
This term refers to the methods by which fire fighters protect merchandise, household goods, and the interiors of buildings from smoke and water damage. Objects are covered with waterproof covers, and water is removed by water vacuums, mops, squeegees, water chutes, and portable pumps. Almost all fire departments carry salvage equipment in their apparatus. Fire departments in some large cities maintain special salvage companies.
Forest Fires
Forest fires, often called wildland fires, are spread by the transfer of heat, in this case to grass, brush, shrubs, and trees. Because it is frequently difficult to extinguish a forest fire by attacking it directly, the principal effort of forest fire fighters is often directed towards controlling its spread by creating a gap, or firebreak, across which fire cannot move. Firebreaks are made, and the fire crews attempt to stop the fire by several methods: trenching, direct attack with hose streams, aerial bombing, spraying of fire-retarding chemicals, and controlled back-burning. As much as possible, advantage is taken of streams, open areas, and other natural obstacles when establishing a firebreak. Wide firebreaks may be dug with ploughs and bulldozers. The sides of the firebreaks are soaked with water or chemicals to slow the combustion process. Some parts of the fire may be allowed to burn themselves out. Fire-fighting crews must be alert to prevent outbreaks of fire on the unburned side of the firebreaks.
Fire-fighting crews are trained and organized to handle fires covering large areas. They establish incident command posts, commissaries, and supply depots. Two-way radios are used to control operations, and aeroplanes are employed to drop supplies as well as chemicals. Helicopters serve as command posts and transport fire fighters and their equipment to areas that cannot be reached quickly on the ground. Some severe wildfires have required more than 10,000 fire fighters to be engaged at the same time. International conferences on wildland fire prevention and fire-fighting have been held with greater frequency in recent years.
Private Fire Protection
Commercial and industrial buildings usually have some sort of internal, or private, fire-protection system installed.
Sprinkler Systems
A sprinkler system is an integrated system of underground and overhead piping, designed in accordance with fire protection engineering standards, and connected to one or more automatic water supplies. The system is usually activated by heat from a fire, and the sprinkler heads then discharge water over the fire area. Sprinkler systems are nearly 100 per cent effective. Many sprinkler systems are supervised electrically from a central station, and alarms are transmitted to a fire department whenever the sprinklers operate or when a valve in the sprinkler system closes for any reason. If a fire-fighting unit arriving at a fire finds that the sprinkler system is not receiving sufficient water and pressure, a pumper is connected to the sprinkler system to supply additional water.
Standpipe Systems
Many high-rise or other large buildings have an internal system of water mains (standpipes) connected to fire-hose stations. Trained occupants or employees of the building management operate the hoses until the fire department arrives. Fire fighters can also connect their hoses to outlets near the fire.
Alarm Systems
Buildings may also be equipped with detection systems that will transmit an alarm. Some detectors are designed to respond to smoke, and others to heat. In many jurisdictions, detection systems are required in public buildings, apartment houses, and sometimes even in private homes.
Two major types of smoke detectors are available. One is an ionization device that contains a small radioactive source for ionizing the air molecules between a pair of electrodes, permitting a very small current to flow between the pair. If smoke particles from a fire enter this space, they reduce the flow of current by adhering to the ionized molecules. The drop in current sets off a buzzer or other alarm. The second type of smoke detector uses a photoelectric cell. In some of these detectors, smoke that enters obscures a steady beam of light; in others, the smoke scatters a light ray from a diode so that the cell can detect it. In either case the change sets off an alarm. The alarm may sound locally, or it may be designed to alert a central station with notification to the fire department. Photoelectric detectors are slower than ionization detectors, and sometimes both principles are combined. Both types can be run by batteries or by building current.
