Fire is the rapid oxidation of a fuel in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. , the most visible portion of the fire, are produced in the combustion reaction when the fuel reaches its ignition point temperature. Flames from hydrocarbon fuels consist primarily of carbon dioxide, water vapor, oxygen, and nitrogen. If hot enough, the gases may become ionized to produce plasma. The color and intensity of the flame depend on the type of fuel and composition of the surrounding gases.
Fire, in its most common form, has the potential to result in conflagration, which can lead to permanent physical damage. It directly impacts land-based ecological systems worldwide. The positive effects of fire include stimulating plant growth and maintaining ecological balance. Its negative effects include hazards to life and property, atmospheric pollution, and water contamination. When fire removes protective vegetation, heavy can cause soil erosion. The burning of vegetation releases nitrogen into the atmosphere, unlike other plant nutrients such as potassium and phosphorus which remain in the Wood ash and are quickly recycled into the soil. This loss of nitrogen produces a long-term reduction in the fertility of the soil, though it can be recovered by nitrogen-fixing plants such as clover, , and ; by decomposition of animal waste and corpses, and by natural phenomena such as lightning.
Fire is one of the four classical elements and has been used by humans in fire worship, in agriculture for clearing land, for cooking, generating heat and light, for signaling, propulsion purposes, smelting, forging, incineration of waste, cremation, and as a weapon or mode of destruction. Various technologies and strategies have been devised to Fire prevention, manage, Fire protection, and extinguish fires, with professional playing a leading role.
"type": "ExternalData", "service": "page", "title": "ROCEEH/Early_fire.map"}
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 or "cool fires", 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.
Another human use for fire in regards to landscape management is its use to clear land for agriculture. Slash-and-burn agriculture is still common across much of tropical Africa, Asia and South America. For small farmers, controlled fires are a convenient way to clear overgrown areas and release nutrients from standing vegetation back into the soil. However, this useful strategy is also problematic. Growing population, fragmentation of forests and warming climate are making the earth's surface more prone to ever-larger escaped fires. These harm ecosystems and human infrastructure, cause health problems, and send up spirals of carbon and soot that may encourage even more warming of the atmosphere – and thus feed back into more fires. Globally today, as much as 5 million square kilometres – an area more than half the size of the United States – burns in a given year.
During the 17th century, a study of combustion was made by Jan Baptist van Helmont who discovered that burning charcoal released a gas sylvestris, or wild spirit. This was subsequently incorporated into Phlogiston theory by Johann Joachim Becher in 1667; a concept that would dominate alchemical thinking for nearly two centuries. It was Antoine Lavoisier who demonstrated that combustion did not involve the release of a substance, but rather something was being taken up. In 1777, Lavoisier proposed a new theory of combustion based on the reaction of a material with a component of air, which he termed oxygène. By 1791, Lavoisier's chemistry concepts had been widely adopted by young scientists, and Phlogiston theory was rejected.
Fire has been used for centuries as a method of torture and execution, as evidenced by death by burning as well as torture devices such as the iron boot, which could be heated over an open fire to the agony of the wearer. In particular, see p. 238.
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 provide electricity for a large percentage of humanity by igniting fuels such as coal, oil or natural gas, then using the resultant heat to boil water into steam, which then drives .
The invention of gunpowder in China led to the fire lance, a flame-thrower weapon dating to around 1000 CE which was a precursor to projectile weapons driven by burning gunpowder. The earliest modern were used by infantry in the First World War, first used by German troops against entrenched French troops near Verdun in February 1915. They were later successfully mounted on armoured vehicles in the Second World War.
Hand-thrown incendiary bombs improvised from glass bottles, later known as Molotov cocktails, were deployed during the Spanish Civil War in the 1930s. During that war, incendiary bombs were deployed against Guernica by Fascist Italian and Nazi Condor Legion air forces that had been created specifically to support Francisco Franco Francoist Spain.
Incendiary bombs were dropped by Axis Powers and Allies during the Second World War, notably on Coventry Blitz, Tokyo, Rotterdam, The Blitz, Hamburg and Dresden. In the latter two cases, were deliberately caused in which a ring of fire surrounding each city was drawn inward by an Vertical draft created by a central cluster of fires. The United States Army Air Force extensively used incendiaries against Japanese targets in the latter months of the war, devastating entire cities constructed primarily of wood and paper houses. The incendiary fluid napalm was used in July 1944, towards the end of the Second World War, although its use did not gain public attention until the Vietnam War.
The Burn 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.
Fires start when a flammable or a combustible material, in combination with a sufficient quantity of an oxidizer such as oxygen gas or another oxygen-rich compound (though non-oxygen oxidizers exist, such as chlorine), 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 triangle. Fire cannot exist without all of these elements in place and in the right proportions. For example, a flammable liquid will start burning only if the fuel and oxygen are in the right proportions.
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. If the oxidizer is oxygen from the surrounding air, the presence of a force of gravity, or of some similar force caused by acceleration, is necessary to produce convection, which removes combustion products and brings a supply of oxygen to the fire. Without gravity, a fire rapidly surrounds itself with its own combustion products and non-oxidizing gases from the air, which exclude oxygen and the fire. Because of this, the risk of fire in a spacecraft is small when it is Orbital maneuver in inertial flight. This does not apply if oxygen is supplied to the fire by some process other than thermal convection.
Fire can be fire protection by removing any one of the elements of the fire tetrahedron. Consider a natural gas flame, such as from a stove-top burner. The fire can be extinguished by any of the following:
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 stoichiometry 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.
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 with hydrogen, and hydrazine with dinitrogen tetroxide. Hydrogen and hydrazine/UDMH flames are similarly pale blue, while burning boron and its compounds, evaluated in mid-20th century as a Zip fuel for Jet engine and , emits intense green flame, leading to its informal nickname of "Green Dragon".
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 and 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 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, 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 may go out if not moved steadily, as the CO2 from combustion does not disperse as readily 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 sufficiently evenly distributed that soot is not formed and complete combustion occurs.
Experiments by NASA reveal that 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 micro gravity when compared to normal gravity conditions. These discoveries have potential applications in applied science and Private industry, especially concerning fuel efficiency.
The early detection of a wildfire outbreak can be performed by a fire lookout observing from a tower constructed for that purpose. The use of these towers peaked in 1938 and has been in decline since that time; most of the fire surveillance work is now performed using and aircraft. Fire suppression aircraft guided by a lookout can be used to help manage wildfires. These are primarily used in support of ground crews
Wildfire prevention programs around the world may employ techniques such as wildland fire use and prescribed or . Wildland fire use refers to any fire of natural causes that is monitored but allowed to burn. Controlled burns are fires ignited by government agencies under less dangerous weather conditions.
Fire prevention is intended to reduce sources of ignition. Fire prevention also includes education to teach people how to avoid causing fires. Buildings, especially schools and tall buildings, often conduct to inform and prepare citizens on how to react to a building fire. Purposely starting destructive fires constitutes arson and is a crime in most jurisdictions.
Model require passive fire protection and active fire protection systems to minimize damage resulting from a fire. A common form of active fire protection is . 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.
Where fire prevention and fire protection have failed to prevent damage, fire insurance can mitigate the financial impact.
The use of a pyre as a Funeral practice dates back to at least the Ancient Roman period in the West, and to about 4,000 years ago on the Indian subcontinent. Cremation of corpses is a tradition long practiced in some cultures, including Hindu. After early religious resistance in some countries, in the 19th century this practice became more widespread and is now commonplace. In some nations, suicide by self-immolation remains common.
The symbology of fire remains important to the present day. Where wood is plentiful, the bonfire can be used for celebration purposes, in many cases as part of a tradition. An example is Guy Fawkes Night in England. The barbecue is a fire-based cultural tradition in the United States. The fiery ignition of fireworks has become a modern tradition to celebrate the arrival. In contrast, book burning has been used as a form of protest, whether for political, religious, or moral reasons. The act of "burning in effigy" has a similar role, as in the annual burning of Judas ritual.
Humans lack an instinctual fascination with fire, yet in modern societies adults can become drawn to it out of curiosity. In societies that are dependent on daily fire use, children lose interest in fire at about age seven due to regular exposure. Arson is the act of intentionally setting fire to a property. A separate but related behavior is pyromania, which is classified as an impulse-control disorder where individuals repeatedly fail to resist impulses to deliberately start fires. In contrast is pyrophobia, an irrational fear of fire. This anxiety disorder is a less common phobia.
Use in war
Productive use for energy
Physical properties
Chemistry
Flame
Typical adiabatic temperatures
Fire science
Ecology
Firefighting
Management, prevention and protection systems
In culture
See also
Notes
Citations
Further reading
External links
|
|