Fire For other uses, see Fire (disambiguation). A forest fire A video showing fire ignite and extinguish Fire is the rapid oxidation of a combustible material releasing heat, light, and various reaction products such as carbon dioxide and water.^[1] If hot enough, the gases may become ionized to produce plasma.^[2] Depending on the substances alight, and any impurities outside, the color of the flame and the fire's intensity might vary. Fire in its most common form can result in conflagration, which has the potential to cause physical damage through burning. * 3 Typical temperatures of fires and flames * 6 Fire fuel * 7 Fire protection and prevention The fire tetrahedron Fires start when a flammable and/or a combustible material, in combination with sufficient quantity of an oxidizer such as oxygen gas or another oxygen-rich compound (though non-oxygen oxidizers exist that can replace oxygen), is exposed to a source of heat or ambient temperature above the flash point for the fuel/oxidizer mix, and is able to sustain a rate of rapid oxidation that produces a chain reaction. This is commonly called the fire tetrahedron. Fire cannot exist without all of these elements being in place and in the right proportions (though as previously stated, another strong oxidizer can replace oxygen). For example, a flammable liquid will start burning only if the fuel and oxygen are in the right proportions. Some fuel-oxygen mixes may require a catalyst; a substance that is not directly involved in any chemical reaction during combustion, but which enables the reactants to combust more readily. Once ignited, a chain reaction must take place whereby fires can sustain their own heat by the further release of heat energy in the process of combustion and may propagate, provided there is a continuous supply of an oxidizer and fuel. Fire can be extinguished by removing any one of the elements of the fire tetrahedron. Consider a natural gas flame, such as from a stovetop burner. The fire can be extinguished by any of the following: * application of water, which removes heat from the fire faster than the fire can produce it (similarly, blowing hard on a flame will displace the heat of the currently-burning gas from its fuel source, to the same end), or In contrast, fire is intensified by increasing the overall rate of combustion. Methods to do this include balancing the input of fuel and oxidizer to stoichiometric proportions, increasing fuel and oxidizer input in this balanced mix, increasing the ambient temperature so the fire's own heat is better able to sustain combustion, or providing a catalyst; a non-reactant medium in which the fuel and oxidizer can more readily react. A flame is a mixture of reacting gases and solids emitting visible and infrared light, the frequency spectrum of which depends on the chemical composition of the burning material and intermediate reaction products. In many cases, such as the burning of organic matter, for example wood, or the incomplete combustion of gas, incandescent solid particles called soot produce the familiar red-orange glow of 'fire'. This light has a continuous spectrum. Complete combustion of gas has a dim blue color due to the emission of single-wavelength radiation from various electron transitions in the excited molecules formed in the flame. Usually oxygen is involved, but hydrogen burning in chlorine also produces a flame, producing hydrogen chloride (HCl). Other possible combinations producing flames, amongst many, are fluorine and hydrogen, and hydrazine and nitrogen tetroxide. The glow of a flame is complex. Black-body radiation is emitted from soot, gas, and fuel particles, though the soot particles are too small to behave like perfect blackbodies. There is also photon emission by de-excited atoms and molecules in the gases. Much of the radiation is emitted in the visible and infrared bands. The color depends on temperature for the black-body radiation, and on chemical makeup for the emission spectra. The dominant color in a flame changes with temperature. The photo of the forest fire is an excellent example of this variation. Near the ground, where most burning is occurring, the fire is white, the hottest color possible for organic material in general, or yellow. Above the yellow region, the color changes to orange, which is cooler, then red, which is cooler still. Above the red region, combustion no longer occurs, and the uncombusted carbon particles are visible as black smoke. [edit] Typical temperatures of fires and flames A Fire at 1/4000th of a second Main article: Fossil record of fire The fossil record of fire first appears with the establishment of a land-based flora in the Middle Ordovician period, 470 million years ago,^[10] permitting the accumulation of oxygen in the atmosphere as never before, as the new hordes of land plants pumped it out as a waste product. When this concentration rose above 13%, it permitted the possibility of wildfire. Wildfire is first recorded in the Late Silurian fossil record, 420 million years ago, by fossils of charcoalified plants.^[11] Apart from a controversial gap in the Late Devonian, charcoal is present ever since.^[11] The level of atmospheric oxygen is closely related to the prevalence of charcoal: clearly oxygen is the key factor in the abundance of wildfire.^[12] Fire also became more abundant when grasses radiated and became the dominant component of many ecosystems, around 6 to 7 million years ago;^[13] this kindling provided tinder which allowed for the more rapid spread of fire.^[12] These widespread fires ma y have initiated a positive feedback process, whereby they produced a warmer, drier climate more conducive to fire.^[12] Main article: Control of fire by early humans The fire miracle of Saint Peter Martyr by Antonio Vivarini. The ability to control fire was a major change in the habits of early humans. Making fire to generate heat and light made it possible for people to cook food, increasing the variety and availability of nutrients. The heat produced would also help people stay warm in cold weather, enabling them to live in cooler climates. Fire also kept nocturnal predators at bay. Evidence of cooked food is found from 1.9 million years ago, although fire was probably not used in a controlled fashion until 400,000 years ago.^[12] Evidence becomes widespread around 50 to 100 thousand years ago, suggesting regular use from this time; interestingly, resistance to air pollution started to evolve in human populations at a similar point in time.^[12] The use of fire became progressively more sophisticated, with it being used to create charcoal and to control wildlife from 'tens of thousands' of years ago.^[12] By the Neolithic Revolution^[citation needed], during the introduction of grain-based agriculture, people all over the world used fire as a tool in landscape management. These fires were typically controlled burns or "cool fires"^[citation needed], as opposed to uncontrolled "hot fires" which damage the soil. Hot fires destroy plants and animals, and endanger communities. This is especially a problem in the forests of today where traditional burning is prevented in order to encourage the growth of timber crops. Cool fires are generally conducted in the spring and autumn. They clear undergrowth, burning up biomass that could trigger a hot fire should it get too dense. They provide a greater variety of environments, which encourages game and plant diversity. For humans, they make dense, impassable forests traversable. The first technical application of the fire may have been the extracting and treating of metals^[citation needed]. There are numerous modern applications of fire. In its broadest sense, fire is used by nearly every human being on earth in a controlled setting every day. Users of internal combustion vehicles employ fire every time they drive. Thermal power stations provide electricity for a large percentage of humanity. The use of fire in warfare has a long history. Hunter-gatherer groups around the world have been noted^[citation needed] as using grass and forest fires to injure their enemies and destroy their ability to find food, so it can be assumed that fire has been used in warfare for as long as humans have had the knowledge to control it^[citation needed]. Fire was the basis of all early thermal weapons. Homer detailed the use of fire by Greek commandos who hid in a wooden horse to burn Troy during the Trojan war. Later the Byzantine fleet used Greek fire to attack ships and men. In the First World War, the first modern flamethrowers were used by infantry, and were successfully mounted on armoured vehicles in the Second World War. In the latter war, incendiary bombs were used by Axis and Allies alike, notably on Tokyo, Rotterdam, London, Hamburg and, notoriously, at Dresden, in the latter two cases firestorms were deliberately caused in which a ring of fire surrounding eac h city^[citation needed] was drawn inward by an updraft caused by a central cluster of fires. The United States Army Air Force also extensively used incendiaries against Japanese targets in the latter months of the war, devastating entire cities constructed primarily of wood and paper houses. In the Second World War, the use of napalm and molotov cocktails was popularized, though the former did not gain public attention until the Vietnam War. More recently many villages were burned during the Rwandan Genocide. [edit] Fire fuel A coal-fired power station in the People's Republic of China Setting fuel aflame releases usable energy. Wood was a prehistoric fuel, and is still viable today. The use of fossil fuels, such as petroleum, natural gas and coal, in power plants supplies the vast majority of the world's electricity today; the International Energy Agency states that nearly 80% of the world's power comes from these sources.^[14] The fire in a power station is used to heat water, creating steam that drives turbines. The turbines then spin an electric generator to produce electricity. The unburnable solid remains of a combustible material left after a fire is called clinker if its melting point is below the flame temperature, so that it fuses and then solidifies as it cools, and ash if its melting point is above the flame temperature. [edit] Fire protection and prevention Main articles: Fire protection and Wildfire#Prevention A structure fire Fire fighting services are provided in most developed areas to extinguish or contain uncontrolled fires. Trained firefighters use fire apparatus, water supply resources such as water mains and fire hydrants or they might use A and B class foam depending on what is feeding the fire. Fire prevention is intended to reduce sources of ignition, and is partially focused on programs to educate people from starting fires.^[15] Buildings, especially schools and tall buildings, often conduct fire drills to inform and prepare citizens on how to react to a building fire. Purposely starting destructive fires constitutes arson and is a criminal offense in most jurisdictions. Model building codes require passive fire protection and active fire protection systems to minimize damage resulting from a fire. The most common form of active fire protection is fire sprinklers. To maximize passive fire protection of buildings, building materials and furnishings in most developed countries are tested for fire-resistance, combustibility and flammability. Upholstery, carpeting and plastics used in vehicles and vessels are also tested. Disability-adjusted life year for fires per 100,000 inhabitants in 2004.^[16] Fire portal * Colored fire * Fire (classical element) * Fire investigation * Fire lookout (tower) * Fire pit * Fire whirl * Fire worship 1. ^ Glossary of Wildland Fire Terminology, National Wildfire Coordinating Group, November 2008, http://www.nwcg.gov/pms/pubs/glossary/pms205.pdf, retrieved 2008-12-18 2. ^ Helmenstine, Anne Marie, What is the State of Matter of Fire or Flame? Is it a Liquid, Solid, or Gas?, About.com, http://chemistry.about.com/od/chemistryfaqs/f/firechemistry.htm, retrieved 2009-01-21 11. ^ ^a ^b Scott, C.; Glasspool, J. (Jul 2006). "The diversification of Paleozoic fire systems and fluctuations in atmospheric oxygen concentration" (Free full text). Proceedings of the National Academy of Sciences of the United States of America 103 (29): 10861–10865. doi:10.1073/pnas.0604090103. ISSN 0027-8424. PMID 16832054. PMC 1544139. http://www.pnas.org/cgi/pmidlookup?view=long&pmid=16832054. edit 12. ^ ^a ^b ^c ^d ^e ^f Bowman, M.; Balch, K.; Artaxo, P.; Bond, J.; Carlson, M.; Cochrane, A.; D'Antonio, M.; Defries, S. et al. (Apr 2009). "Fire in the Earth System". Science 324 (5926): 481. doi:10.1126/science.1163886. ISSN 0036-8075. PMID 19390038. edit 15. ^ Fire & Life Safety Education, Manitoba Office of the Fire Commissioner * Karki, Sameer (2002) (PDF), Community Involvement in and Management of Forest Fires in South East Asia, Project FireFight South East Asia, http://www.asiaforests.org/doc/resources/fire/pffsea/Report_Community.pdf, retrieved 2009-02-13 * Haung, Kai. 2009. Population and Building Factors That Impact Residential Fire Rates in Large U.S. Cities. Applied Research Project. Texas State University. http://ecommons.txstate.edu/arp/287/ Search Wikimedia Commons Wikimedia Commons has media related to: Fire Search Wikiquote Wikiquote has a collection of quotations related to: Fire * How Fire Works at HowStuffWorks * What exactly is fire? from The Straight Dope * On Fire, an Adobe Flash-based science tutorial from the NOVA (TV series) * Early human fire mastery revealed BBC article on archaeological discoveries * moebuildingcontrol.co.uk - UK Guidance on fire safety codes and fire engineering * Smokey Bear - Prevent Wildfires * Fun Uses with Fire with a Rubens' Tube Retrieved from "http://en.wikipedia.org/wiki/Fire" Categories: Fire