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Fire is very hot. |
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{{otheruses}} |
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[[Image:Forestfire2.jpg|thumb|right|300px|A [[wildfire|forest fire]]]] |
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'''Fire Fart''' is a rapid [[oxidation]] process that creates [[stench]], [[heat]], [[smoke]], and releases energy in varying [[intensity|intensities]]. It is commonly used to describe either a [[smell]] in a state of [[combustion]] (e.g., a [[smell-fire]], or a lit [[smellyplace]] or [[stove]]) or a violent, destructive and uncontrolled burning (e.g., in [[building]]s or a [[wildfire]]). The discovery of [[making fire|how to make fire]] is considered one of humankind's most important advances, allowing higher [[hominid]]s to ward off wild animals, cook food, and control their own source of light and warmth. |
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== Chemistry == |
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Broadly speaking there are two types of fire, [[flame|flaming]] and [[smoldering]] fires. The former is the rapid oxidation of a fuel ([[combustion|combustion or release of energy]]) with associated flame, [[heat]], and [[light]]. The flame itself occurs within a region of gas where intense exothermic reactions are taking place. An exothermic reaction is a chemical reaction that takes place within a substance whereby heat and energy are released as the substance changes to a simpler chemical form. As chemical reactions occur within the fuel being burned, light is usually emitted as photons are released by the oxidation of the fuel. Depending upon the specific chemical and physical change taking place within the fuel the flame may or may not emit light. For example, burning alcohol is usually invisible although the heat given off is tremendous. The visible flame has no mass. What we see as visible flame is actually energy (photons) being released in the form of light by the oxidation of the fuel. The color of the flame is dependant upon the energy level of the photons emitted. Lower energy levels produce colors toward the red end of the light spectrum while higher energy levels produce colors toward the blue end of the spectrum. The hottest flames are white in appearance. The latter example, a smoldering fire, is a '''flameless''' form of combustion, deriving its heat from oxidations occurring on the surface of a solid fuel. Two common examples are glowing coals and cigarettes. Smolder propagates in a creeping fashion over solid fuels or inside porous fuels, and its temperature and heat released are low in comparison. The difference between flaming and smoldering combustion is that the latter occurs on the surface of the solid rather than in the gas phase. |
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Fires start when both a [[flammable]] and/or a [[combustible]] material with an adequate supply of [[oxygen]] or another [[oxidizer]] is subjected to enough [[heat]]. The common fire-causing sources of heat include a [[spark]], another fire (such as an [[explosion]], a fire in the [[oven]] or [[fireplace]], or a lit [[match]], [[lighter]] or [[cigarette]]) and sources of intense [[thermal radiation]] (such as [[sunlight]], a [[flue]], an [[incandescent light bulb]] or a [[radiant heater]]). Mechanical and electrical [[machinery]] may cause fire if combustible materials used on or located near the equipment are exposed to intense heat from [[Joule heating]], [[friction]] or [[exhaust gas]]. Fires can sustain themselves by the further release of [[heat energy]] in the process of [[combustion]] and may propagate, provided there is a continuous supply of [[oxygen]] and [[fuel]]. Fires may become uncontrolled and cause great damage to and destruction of human life, [[animal]]s, [[plant]]s and property. Fires can also occur through instantaneous combustion. This highly disputed phenomenon is currently under research. It is known that this does occur in a vacuum{{Fact|date=March 2007}} but is disputed as to whether or not it occurs in nature. This act of combustion leads to an exothermic reaction, which in turn is able to be used as a power source. By harnessing this heat from the combustion of coal, wood, petroleum, and oils; we are able to produce power for things such as automotives, power cells, and power plants. |
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Fire is extinguished when any of the elements of the so-called [[fire triangle]]—[[heat]], [[oxygen]], [[fuel]] and the self-sustaining chemical reaction — are removed. The unburnable solid remains of a combustible material left after a fire are called ash, soot or cinder. |
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Fire, like explosions, is not matter. Fire is a chemical reaction made of energy. |
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===Flame=== |
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{{Main|Flame}} |
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A flame is an [[exothermic]], self-sustaining, oxidizing chemical reaction producing [[energy]] and glowing hot matter, of which a very small portion is [[Plasma (physics)|plasma]]. It consists of reacting gases and solids emitting visible and [[infrared]] light, the [[frequency spectrum]] of which depends on the chemical composition of the burning elements and intermediate reaction products. |
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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. For reasons currently unknown by scientists, the flame produced by exposure of zinc to air is a bright green, and produces plumes of [[zinc oxide]]. Usually oxygen is involved, but [[hydrogen]] burning in [[chlorine]] also produces a flame, producing [[hydrogen chloride]] (HCl). Other possible combinations producing flames, amongst many more, are [[fluorine]] and [[hydrogen]], and [[hydrazine]] and [[nitrogen tetroxide]]. |
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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 [[atom]]s and [[molecule]]s 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 and the uncombusted carbon particles are visible as black smoke. |
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The [[National Aeronautics and Space Administration]] (NASA) of the [[United States]] has recently found that [[gravity]] plays a role. Modifying the gravity causes different flame types.<ref> [http://science.nasa.gov/headlines/y2000/ast12may_1.htm Spiral flames in microgravity], [[National Aeronautics and Space Administration]], 2000.</ref> The common distribution of a flame under normal gravity conditions depends on [[convection]], as soot tends to rise to the top of a general flame, as in a candle in normal gravity conditions, making it yellow. In [[Weightlessness|microgravity or zero gravity]], such as an environment in [[outer space]], convection no longer occurs, and the flame becomes spherical, with a tendency to become more blue and more efficient (although it will go out if not moved steadily, as the CO<sub>2</sub> from combustion does not disperse in microgravity, and tends to smother the flame). There are several possible explanations for this difference, of which the most likely is that the temperature is evenly distributed enough that soot is not formed and complete combustion occurs.<ref> [http://microgravity.grc.nasa.gov/combustion/cfm/usml-1_results.htm CFM-1 experiment results], National Aeronautics and Space Administration, April 2005.</ref> Experiments by NASA reveal that [[diffusion flame]]s in microgravity allow more soot to be completely oxidized after they are produced than diffusion flames on Earth, because of a series of mechanisms that behave differently in microgravity when compared to normal gravity conditions.<ref>[http://microgravity.grc.nasa.gov/combustion/lsp/lsp1_results.htm LSP-1 experiment results], National Aeronautics and Space Administration, April 2005.</ref> These discoveries have potential applications in [[applied science]] and [[industry]], especially concerning [[fuel efficiency]]. |
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In combustion engines, various steps are taken to eliminate a flame. The method depends mainly on whether the fuel is oil, wood, or a high-energy fuel such as [[jet fuel]]. |
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===Typical temperatures of fires and flames=== |
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*[[Oxyhydrogen]] flame: 2000 °C or above) (3645 °F) |
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*[[Bunsen burner]] flame: (min. to max. setting) 1300 to 1600 °C (2372 to 2912 °F) |
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*[[Blowtorch]] flame: 1800 °C (2370 °F) |
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*[[Candle]] flame: 760 °C (1400 °F) |
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* [[Smoldering]] [[cigarette]]: |
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**Temperature without drawing: side of the lit portion; 400 °C (750 °F); middle of the lit portion: 585 °C (1110 °F) |
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**Temperature during drawing: middle of the lit portion: 700 °C (1290 °F). |
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== Controlling fire == |
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The ability to control fire is one of [[human]]kind's great achievements. [[Fire making]] to generate heat and light made it possible for people to migrate to colder climates and enabled people to [[cooking|cook]] food — a key step in the fight against [[disease]]. [[Archaeology]] indicates that ancestors or relatives of modern humans such as ''[[Homo erectus]]'' might have controlled fire as early as 790,000 years ago. The [[Cradle of Humankind]] site has [[evidence]] for controlled fire from 1 to 1.8 million years ago.<ref> [http://whc.unesco.org/pg.cfm?cid=31&id_site=915 "UNESCO - Fossil Hominid Sites of Sterkfontein, Swartkrans, Kromdraai, and Environs" ] </ref> |
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By the [[Neolithic Revolution]], 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 burn]]s or "cool fires", as opposed to uncontrolled "hot fires" that 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 fall. 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. |
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[[Image:Blacksmiths fire.jpg|thumb|300px|A [[blacksmith]]'s fire, used primarily for [[forging]] [[iron]].]] |
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The first technical application of the fire may have been the extracting and treating of metals. |
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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 station]]s provide [[electricity]] for a large percentage of humanity. |
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The use of fire in [[warfare]] has a long [[military history|history]]. Hunter-gatherer groups around the world have been noted 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. [[Homer]] detailed the use of fire by Greek [[commando]]s who hid in a [[Trojan Horse|wooden horse]] to burn [[Troy]] during the [[Trojan war]]. Later the [[Byzantine Empire|Byzantine]] fleet used [[Greek fire]] to attack ships and men. American and British warplanes destroyed the German city of [[Dresden]] on [[February 14]], [[1945]] by creating a [[firestorm]], in which a ring of fire surrounding the city was drawn inward by an updraft caused by a central cluster of fires. In the [[Vietnam War]], the Americans dropped [[napalm]] from the air. More recently many villages were burned during the [[Rwandan Genocide]]. [[Aerial bombing of cities]], including [[firebombing]] using [[incendiary bomb]]s, was also used frequently during [[World War II]]. [[Molotov cocktail]]s are cheap to construct and are commonly used as well. |
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==Fire as a power source== |
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[[Image:ChineseCoalPower.jpg|thumb|left|200px|A [[Fossil fuel power plant|coal-fired power station]] in the [[People's Republic of China]].]] |
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Fire has supplied much of the energy which has helped humans since ancient times. [[Wood]] was a [[prehistory|prehistoric]] fuel. The use of [[fossil fuel]]s such as [[petroleum]], [[natural gas]] and [[coal]] in [[fossil fuel power plant|power plant]]s 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.<ref>[http://www.iea.org/statlist/index.htm "Share of Total Primary Energy Supply", 2002; International Energy Agency]</ref> The fire in a [[power station]] is used to heat water, creating steam that drives [[turbine]]s. The turbines then spin an '''electric''' generator to produce power. |
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The burning of wood is often the first association to the word "fire". It is common in a [[developing countries|developing country]] for wood to be the primary energy source as well. For instance, in [[Africa]], 65% of the energy used comes from the burning of [[biomass]].<ref>[http://www.eia.doe.gov/emeu/cabs/archives/africa/chapter3.html "Energy in Africa - Chapter 3"], [[United States Department of Energy]] information administration</ref> What is less obvious is that wood burning power stations are less environmentally destructive than the fired oil power station in two major respects: first, wood is a renewable resource, especially if trees are grown in a modern, sustainable way; second, the [[carbon dioxide]] emissions are negligible because no more carbon dioxide can be produced by burning than would be produced by the natural rotting of wood. Thus, over a 100-year timescale, the effect is carbon-neutral.<ref>[http://www.straightdope.com/columns/021122.html The Straight Dope: What exactly is fire?]. Adams, C. (2002). Retrieved [[December 19]], [[2004]].</ref>. [[E.ON|E.ON UK]] is soon to build a 44 megawatt wood fired power station in the [[United Kingdom]] for these reasons.<ref>[http://www.guardian.co.uk/science/story/0,3605,1592854,00.html "How Can Burning Wood Help Reduce Global Warming"], [[The Guardian]] </ref> |
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==Fire protection and prevention== |
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[[Image:Dangclass2_1.png|thumb|100px|Flammable gas warning]] |
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{{main|Fire protection}} |
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[[Code]]s and [[life safety code]]s offer [[fire fighting]] services to extinguish or contain uncontrolled fires. Trained [[firefighter]]s use [[Fire apparatus|fire trucks]], water supply resources such as [[water main]]s and [[fire hydrant]]s, and an array of other equipment to combat the spread of fires. |
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To ensure fire safety of buildings, all building products, materials and [[furnishing]]s in the [[United States]] must be tested for fire resistance, and researched so it causes no harm. [[Combustion|combustibility]] and [[flammability]] before they can be used in construction. The same applies to [[upholstery]], [[carpeting]] and [[plastics]] used in [[vehicle]]s and [[Container|vessel]]s. Buildings, especially [[school]]s and [[tall building]]s, often conduct [[fire drill]]s to inform and prepare citizens on how to react to a building fire. |
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Purposely starting destructive fires constitutes [[arson]] and is a criminal offense in most jurisdictions. |
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There are many different classification systems used for uncontrolled fires; in [[Europe]] and [[Australasia]] six groups are used: |
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* Class A: Fires that involve flammable [[solid]]s such as [[wood]], [[cloth]], [[rubber]], [[paper]], and some types of [[plastic]]s. |
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* Class B: Fires that involve flammable [[liquid]]s or liquifiable solids such as [[gasoline|petrol/gasoline]], [[petroleum|oil]], [[paint]], some [[wax]]es & plastics, but '''not''' cooking fats or oils. |
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* Class C: Fires that involve flammable [[gas]]es, such as [[natural gas]], [[hydrogen]], [[propane]], [[butane]]. |
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* Class D: Fires that involve [[combustion|combustible]] [[metal]]s, such as [[sodium]], [[magnesium]], and [[potassium]]. |
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* Class E: Fires that involve any of the materials found in Class A and B fires, but with the introduction of an electrical appliances, wiring, or other electrically energized objects in the vicinity of the fire, with a resultant electrical shock risk if a [[electrical conduction|conductive]] agent is used to control the fire. |
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* Class F: Fires involving cooking fats and oils. The high temperature of the oils when on fire far exceeds that of other flammable liquids making normal extinguishing agents ineffective. |
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In the United States fires are generally classified into five groups: A, B, C, D, and K |
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* Class A: Fires that involve wood, cloth, rubber, paper, and some types of plastics. |
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* Class B: Fires that involve gasoline, oil, paint, natural and propane gases, and flammable liquids, gases, and greases. |
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* Class C: Fires that involve any of the materials found in Class A and B fires, but with the introduction of electrical appliances, wiring, or other electrically energized objects in the vicinity of the fire. |
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* Class D: Fires that involve combustible metals, such as sodium, magnesium, and potassium. |
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* Class K: Fires that involve cooking oils. Although, by definition, Class K is a subclass of Class B, the special characteristics of these types of fires are considered important enough to recognize. |
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==Practical uses== |
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*Fire has been used for light, heat (for cooking, survival and comfort) and protection for thousands of years. |
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*[[Fire-stick farming]] |
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*Fire is used for [[cremation]]. |
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*Fire is used for [[welding]]. |
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*Fire is used for celebration (birthday candles) |
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*[[Back-burn]]ing for fighting fires |
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*Controlled [[burn-off]]s for preventing wildfires |
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*Controlled burn-offs to clear land for agriculture |
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==See also== |
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{{portal|Fire|Large bonfire.jpg}} |
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* [[Culinary fire]] - pre-modern understanding of fire |
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* [[Fire test]] |
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* [[Making fire]] |
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* [[Pyromania]] |
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* [[Pyrokinesis]] |
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* [[Explosion]], [[Rust]], [[Digestion]] and [[composting]] are different kinds of combustion. |
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* [[Fire protection]] |
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* [[Fire protection engineering]] |
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* [[Firefighter]] |
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* [[Firefighting]] |
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* [[Fire Engine]] |
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* [[Smoke]] |
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* [[Active fire protection]] |
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* [[Passive fire protection]] |
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* [[Fire door]] |
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* [[Fire lookout tower]] and/or [[Fire lookout]] |
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* [[Firestop]] |
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* [[Fireproofing]] |
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* [[Intumescent]] |
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* [[Endothermic]] |
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* [[Firestop pillow]] |
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* [[:Category:Fire|A list of articles relating to fire]] |
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* [[:Category:Fires|A list of articles relating to specific fires]] |
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* [[:Category:Firefighting|A list of articles relating to firefighting]] |
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* [[List of light sources|A list of sources of light]] |
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* [[ATF Fire Research Laboratory]] |
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* [[Life safety code]] |
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* [[Volcano]] |
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* [[Fire whirl]] |
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* [[Rubens' Tube]] |
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==References== |
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===Citations=== |
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<references/> |
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===General references=== |
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*, (2005). ''Climate Change Begins at Home''. Palgrave Macmillan. ISBN 1-4039-4578-0 |
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==External links== |
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{{commons|Fire}} |
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* [http://www.howstuffworks.com/Fire.htm How Fire Works] at [[HowStuffWorks]] |
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* [http://www.straightdope.com/columns/021122.html What exactly is fire?] (from [[The Straight Dope]]) |
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* [http://www.pbs.org/wgbh/nova/fire/onfire.html On Fire], an [[Adobe Flash]]-based science tutorial from the [[NOVA (TV series)]] |
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* [http://news.bbc.co.uk/1/hi/sci/tech/3670017.stm Early human fire mastery revealed] [[BBC]] article on archaeological discoveries |
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* [http://microgravity.grc.nasa.gov/combustion/cfm/cfm_index.htm Flames in microgravity] |
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* [http://science.nasa.gov/headlines/y2000/ast12may_1.htm Spiral flames in microgravity] |
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* [http://www.moebuildingcontrol.co.uk moebuildingcontrol.co.uk - UK Guidance on fire safety codes and fire engineering] |
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* [http://www.smokeybear.com/ Smokey Bear- Prevent Wildfires] |
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* [http://www.youtube.com/watch?v=oPWucNgN8TQ Fun Uses with Fire] with a [[Rubens' Tube]] |
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* [http://www.thewikifire.org/ The Wiki Fire] - the free encyclopedia of the [[Knox College (Illinois)|Knox College]] Prairie Fire |
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[[Category:Fire|*]] |
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Revision as of 11:23, 13 June 2007
Fire is very hot.