Fire: Difference between revisions
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Fire is really cold and it can't kill you. |
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{{Otheruses}} |
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[[Image:Firefighting exercise.jpg|thumb|350px|[[United States Air Force|U.S. Air Force]] Airmen from the 20th Civil Engineer Squadron Fire Protection Flight neutralize a live fire during a field training exercise.]] |
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'''Fire''' is the [[heat]] and [[light]] energy released during a [[chemical reaction]] (in particular, a [[combustion|combustion reaction]]). 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]], and has the potential to cause physical damage through [[burning]]. |
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==Chemistry== |
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===Chemical Reaction=== |
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[[Image:Fire tetrahedron.svg|thumb|150px|The fire tetrahedron]] |
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Fires start when a [[flammable]] and/or a [[combustible]] material with an adequate supply of [[oxygen]] or another [[oxidizer]] is subjected to enough [[heat]] and is able to sustain a [[chain reaction]]. This is commonly called the [[fire tetrahedron]]. No fire can exist without all of these elements being in place. |
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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]]. |
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Fire can be [[fire protection|extinguished]] by removing any one of the elements of the fire tetrahedron. Fire extinguishing by the application of water acts by removing heat from the fuel faster than combustion generates it. Application of [[carbon dioxide]] is intended primarily to starve the fire of oxygen. A forest fire may be fought by starting smaller fires in advance of the main blaze, to deprive it of fuel. Other gaseous fire suppression agents, such as [[Bromotrifluoromethane|halon]] or [[HFC-227]], interfere with the chemical reaction itself. |
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===Flame=== |
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[[Image:Log in fireplace.jpg|thumb|225px|left|A log on fire]] |
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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. 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|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 no longer occurs, 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 or above (3645 °F) <ref> [http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PFLDAS000009000008001577000001&idtype=cvips&gifs=yes "Flame Temperature Measurement"] </ref> |
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* [[Bunsen burner]] flame: 1300 to 1600 °C (2372 to 2912 °F) <ref> [http://www.derose.net/steve/resources/engtables/flametemp.html "Flame Temperatures"] </ref> |
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* [[Blowtorch]] flame: 1,300 °C (2372 °F) <ref> [http://www.cooperhandtools.com/europe/sales_literature/documents/WellerPyropen_GB.pdf "Pyropen Cordless Soldering Irons"] </ref> |
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* [[Candle]] flame: 1000 °C (1832 °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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** Always hotter in the middle. |
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====Temperatures of flames by appearance==== |
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The temperature of flames with carbon particles emitting light can be assessed by their color:<ref>"A Book of Steam for Engineers", The Stirling Company, 1905</ref> |
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* Red |
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** Just visible: 525 °C (977 °F) |
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** Dull: 700 °C (1290 °F) |
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** Cherry, dull: 800 °C (1470 °F) |
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** Cherry, full: 900 °C (1650 °F) |
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** Cherry, clear: 1000 °C (1830 °F) |
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* Orange |
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** Deep: 1100 °C (2010 °F) |
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** Clear: 1200 °C (2190 °F) |
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* White |
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** Whitish: 1300 °C (2370 °F) |
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** Bright: 1400 °C (2550 °F) |
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** Dazzling: 1500 °C (2730 °F) |
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==Controlling fire== |
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[[Image:Forestfire2.jpg|thumb|225px|A [[wildfire|forest fire]]]] |
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The ability to [[control of fire by early humans|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 [[cooking|cook]] food, increasing the variety and availability of nutrients. Fire also kept nocturnal predators at bay. [[Archaeology]] indicates that ancestors or relatives of modern humans 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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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 [[Conventional warfare|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. In the First World War, the first modern [[flamethrower]]s 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 Rotterdam, London, Hamburg and, notoriously, at [[Dresden]], in the latter two cases [[firestorm]]s were deliberately caused in which a ring of fire surrounding each city 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 cocktail]]s was popularized, though the former did not gain public attention until the [[Vietnam War]]. More recently many villages were burned during the [[Rwandan Genocide]]. |
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==Fire fuel== |
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[[Image:ChineseCoalPower.jpg|thumb|left|A [[Fossil fuel power plant|coal-fired power station]] in the [[People's Republic of China]]]] |
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Setting [[fuel]] aflame releases usable energy. [[Wood]] was a [[prehistory|prehistoric]] fuel, and is still viable today. 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 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.{{-}} |
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==Fire protection and prevention== |
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{{main|Fire protection}} |
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[[Image:FirePhotography.jpg|thumb|right|A [[structure fire]]]] |
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[[Fire fighting]] services are provided in most developed areas to extinguish or contain uncontrolled fires. Trained [[firefighter]]s use [[Fire apparatus]], water supply resources such as [[water main]]s and [[fire hydrant]]s or they might use A and B class foam depending on what is feeding the fire. An array of other equipment to combat the spread of fires. |
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''Fire prevention'' is intended to reduce sources of ignition, and is partially focused on programs to educate people from starting fires.<ref>[http://www.firecomm.gov.mb.ca/safety_education_nero_and_ashcan.html#6 Fire & Life Safety Education], [[Manitoba]] Office of the Fire Commissioner</ref> Buildings, especially [[school]]s and [[tall building]]s, 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. |
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Model building [[code]]s require [[passive fire protection]] and [[active fire protection]] systems to minimize [[Fire damage|damage resulting from a fire]]. The most common form of active fire protection is [[fire sprinkler]]s. To maximize passive fire protection of buildings, [[building material]]s and [[furnishing]]s in most developed countries are tested for [[Fire-resistance rating|fire-resistance]], [[Combustion|combustibility]] and [[flammability]]. [[Upholstery]], [[carpeting]] and [[plastics]] used in [[vehicle]]s and [[Containerization|vessel]]s are also tested. |
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==Practical uses== |
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[[Image:Blacksmiths fire.jpg|thumb|225px|right|A [[blacksmith]]'s fire is used primarily for [[forging]] [[iron]].]] |
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Fire is or has been used: |
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* For light, heat (for cooking, survival and comfort), and protection |
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* As a [[napalm|weapon of warfare]], especially during [[Early thermal weapons|ancient and medieval times]]. |
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* For [[fire-stick farming]] |
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* For [[cremation]] |
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* For [[welding]] |
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* For celebration (such as, birthday candles) |
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* For religious observances |
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* For [[back-burn]]ing in fighting fires |
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* For controlled [[burn-off]]s for preventing [[wildfire]]s |
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* For burn-offs to clear land for agriculture or for promoting new growth |
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* For recreational use as a [[campfire]] or [[bonfire]] |
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==See also== |
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{{portal|Fire|Large bonfire.jpg}} |
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<div style="column-count:3;-moz-column-count:3;"> |
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* [[Active fire protection]] |
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* [[:Category:Fire|A list of articles relating to fire]] |
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* [[:Category:Firefighting|A list of articles relating to firefighting]] |
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* [[:Category:Fires|A list of articles relating to specific fires]] |
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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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* [[Colored fire]] - common and cheap chemicals by which to color a fire |
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* [[Endothermic]] |
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* [[Explosion]], [[Rust]], [[Digestion]] and [[composting]] are different kinds of combustion. |
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* [[Fire door]] |
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* [[Fire damage]] |
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* [[Fire lookout tower]] and/or [[Fire lookout]] |
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* [[Fireproofing]] |
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* [[Fire protection]] |
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* [[Fire protection engineering]] |
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* [[Firestop]] |
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* [[Firestop pillow]] |
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* [[Fire pit]] |
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* [[Fire test]] |
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* [[Fire whirl]] |
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* [[Fire worship]] |
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* [[Flame test]] - using flame colors to identify common metals |
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* [[Intumescent]] |
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* [[Life safety code]] |
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* [[Lightning]] |
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* [[Making fire]] |
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* [[Passive fire protection]] |
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* [[Plasma]] |
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* [[Pyromania]] |
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* [[Pyrokinesis]] |
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* [[Rubens' Tube]] |
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* [[Smoke]] |
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* [[Volcano]] |
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</div> |
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== References == |
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{{reflist}} |
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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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[[Category:Fire|*]] |
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[[af:Vuur]] |
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[[ar:نار (طبيعة)]] |
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[[an:Fuego]] |
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[[arc:ܢܘܪܐ]] |
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[[ay:Nina]] |
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[[be-x-old:Агонь]] |
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[[bg:Огън]] |
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[[ca:Foc]] |
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[[cs:Oheň]] |
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[[ch:Guafi]] |
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[[co:Focu]] |
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[[za:Feiz]] |
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[[cy:Tân]] |
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[[da:Ild]] |
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[[pdc:Feier]] |
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[[de:Feuer]] |
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[[el:Φωτιά]] |
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[[es:Fuego]] |
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[[eo:Fajro]] |
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[[eu:Su]] |
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[[fa:آتش]] |
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[[fr:Feu]] |
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[[fur:Fûc]] |
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[[gd:Teine]] |
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[[gl:Lume]] |
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[[zh-classical:火]] |
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[[ko:불]] |
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[[hr:Vatra]] |
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[[io:Fairo]] |
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[[id:Api]] |
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[[is:Eldur]] |
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[[it:Fuoco (fisica)]] |
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[[he:אש]] |
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[[jv:Geni]] |
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[[kn:ಬೆಂಕಿ]] |
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[[ku:Agir]] |
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[[la:Ignis]] |
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[[lv:Uguns]] |
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[[lb:Feier]] |
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[[lt:Ugnis]] |
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[[lmo:Fööch]] |
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[[hu:Tűz]] |
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[[ml:തീ]] |
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[[ms:Api]] |
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[[cdo:Huōi]] |
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[[mn:Гал]] |
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[[nl:Vuur]] |
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[[cr:Ishkuteu]] |
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[[ja:火]] |
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[[nap:Ffuoco]] |
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[[no:Ild]] |
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[[nn:Eld]] |
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[[pl:Ogień]] |
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[[pt:Fogo]] |
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[[qu:Nina]] |
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[[ru:Огонь]] |
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[[sco:Fire]] |
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[[sq:Zjarri]] |
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[[scn:Focu]] |
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[[simple:Fire]] |
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[[sk:Oheň]] |
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[[sl:Ogenj]] |
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[[sr:Ватра]] |
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[[fi:Tuli]] |
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[[sv:Eld]] |
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[[tl:Apoy]] |
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[[ta:நெருப்பு]] |
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[[te:అగ్ని]] |
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[[th:ไฟ]] |
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[[vi:Lửa]] |
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[[tr:Ateş]] |
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[[uk:Вогонь]] |
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[[ur:آگ]] |
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[[vec:Fógo]] |
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[[wuu:火]] |
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[[yi:פייער]] |
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[[zh-yue:火]] |
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[[bat-smg:Ognis]] |
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[[zh:火]] |
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Revision as of 06:16, 24 November 2008
Fire is really cold and it can't kill you.