======================================================================
= Fire =
======================================================================
Introduction
======================================================================
Fire is the rapid oxidation of a fuel in the exothermic chemical
process of combustion, releasing heat, light, and various reaction
products.
Flames, 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 rainfall 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 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,
peas, and beans; 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 rituals, 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
prevent, manage, mitigate, and extinguish fires, with professional
firefighters playing a leading role.
Etymology
======================================================================
The word 'fire' comes from Old English and has cognates in many
Germanic languages and other Indo-European languages. The
Proto-Germanic nominative form is reconstructed as , descending from
Proto-Indo-European . An alternative spelling existed in Middle
English: ; still preserved in 'fiery'.
The word 'ignite' is derived from the classical Latin 'ignis' meaning
fire. The Greek term for fire, 'pyr', is used in words such as
pyroclastic or pyrotechnic.
Fossil record
===============
The fossil record of fire first appears with the establishment of a
land-based flora in the Middle Ordovician period, . These land plants
contributed large amounts of oxygen to the atmosphere when they
released it 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, , by fossils of charred
plants. Apart from a controversial gap in the Late Devonian, charcoal
is present ever since. The level of atmospheric oxygen is closely
correlated with the amount of charcoal in the fossil record, clearly
pointing to oxygen as the key factor in the prevalence of wildfire.
Fire also became more abundant when grasses became the dominant
component of many ecosystems, around , providing excellent tinder for
more rapid spread of fire. This widespread emergence of wildfire may
have initiated a positive feedback process, whereby they produced a
warmer, drier climate more conducive to fire. Fire made it possible
for humans to live at colder places and dark caves. It also protected
humans against dangerous animals. It caused nutritional changes, it
enabled us to eat with more variation.
Human control
===============
The period of history characterized by the influence of human-caused
fire activity on Earth has been dubbed the pyrocene. This epoch
includes the burning of fossil fuels, especially for technological
uses.
Early human control
=====================
{
"type": "ExternalData",
"service": "page",
"title": "ROCEEH/Early_fire.map"
}
The ability to control fire was a dramatic change in the habits of
early humans. Making fire to generate heat and light made it possible
for people to cook food, simultaneously increasing the variety and
availability of nutrients and reducing disease by killing pathogenic
microorganisms in the food. 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 occasional
cooked food is found from , suggesting it was used in a controlled
fashion. Other sources put the date of regular use at 400,000 years
ago. Evidence becomes widespread around 50 to 100 thousand years ago,
suggesting regular use from this time; resistance to air pollution
started to evolve in human populations at a similar point in time. The
use of fire became progressively more sophisticated, as it was used to
create charcoal and to control wildlife from tens of thousands of
years ago.
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 burns 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.
Later human control
=====================
Throughout much of history, cultures attempted to explain nature and
the properties of matter by proposing a set of four (or five)
classical elements, of which fire formed one of the components. As
scientific understanding developed following the Middle Ages, this
philosophy was replaced by a set of chemical elements and their
interactions. Instead, the classical elements found an equivalency in
the states of matter: solid, liquid, gas, and plasma.
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.
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 by igniting fuels such as coal, oil or
natural gas, then using the resultant heat to boil water into steam,
which then drives turbines.
Use in war
============
The use of fire in warfare has a long history. Fire was the basis of
all early thermal weapons, including incendiary devices, heated
projectiles, and the use of smoke. This class of weapons was
particularly evident during naval battles and siege warfare. The
Byzantine fleet used Greek fire to attack ships and men.
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
flamethrowers 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 German air forces that had been
created specifically to support Franco's Nationalists.
Incendiary bombs were dropped by Axis and Allies during the Second
World War, notably on Coventry, Tokyo, Rotterdam, London, Hamburg and
Dresden. In the latter two cases, firestorms were deliberately caused
in which a ring of fire surrounding each city was drawn inward by an
updraft 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.
Productive use for energy
===========================
Burning fuel converts chemical energy into heat energy; wood has been
used as fuel since prehistory. The International Energy Agency states
that nearly 80% of the world's power has consistently come from fossil
fuels such as petroleum, natural gas, and coal in the past decades.
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. Fire is also used to provide mechanical work
directly by thermal expansion, in both external and internal
combustion engines.
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.
Chemistry
===========
Fire is a chemical process in which a fuel and an oxidizing agent
react, yielding carbon dioxide and water. This process, known as a
combustion reaction, does not proceed directly and involves
intermediates. Although the oxidizing agent is typically oxygen, other
compounds are able to fulfill the role. For instance, chlorine
trifluoride is able to ignite sand.
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 tetrahedron. 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. Some fuel-oxygen mixes may require a
catalyst, a substance that is not consumed, when added, 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. 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 extinguish the fire. Because of this, the
risk of fire in a spacecraft is small when it is coasting in inertial
flight. This does not apply if oxygen is supplied to the fire by some
process other than thermal convection.
Fire can be extinguished 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:
* turning off the gas supply, which removes the fuel source;
* covering the flame completely, which smothers the flame as the
combustion both uses the available oxidizer (the oxygen in the air)
and displaces it from the area around the flame with CO2;
* application of an inert gas such as carbon dioxide, smothering the
flame by displacing the available oxidizer;
* 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
* application of a retardant chemical such as Halon (largely banned in
some countries ) to the flame, which retards the chemical reaction
itself until the rate of combustion is too slow to maintain the chain
reaction.
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.
Flame
=======
A diffusion flame is a mixture of reacting gases and solids emitting
visible, infrared, and sometimes ultraviolet light, the frequency
spectrum of which depends on the chemical composition of the burning
material and intermediate reaction products. During the burning of
hydrocarbons, 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 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 high energy fuel for
jet and rocket engines, 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 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 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 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
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 diffusion flames 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 industry, especially concerning fuel efficiency.
Typical adiabatic temperatures
================================
The adiabatic flame temperature of a given fuel and oxidizer pair is
that at which the gases achieve stable combustion.
* Oxy-dicyanoacetylene 4990 C
* Oxy-acetylene 3997 C
* Oxyhydrogen 3473 C
* Air-acetylene 2500 C
* Blowtorch (air-MAPP gas) 2020 °C
* Bunsen burner (air-natural gas) 1300 to
* Candle (air-paraffin) 1000 °C
Fire science
======================================================================
Fire science is a branch of physical science which includes fire
behavior, dynamics, and combustion. Applications of fire science
include fire protection, fire investigation, and wildfire management.
Ecology
=========
Every natural ecosystem on land has its own fire regime, and the
organisms in those ecosystems are adapted to or dependent upon that
fire regime. Fire creates a mosaic of different habitat patches, each
at a different stage of succession. Different species of plants,
animals, and microbes specialize in exploiting a particular stage, and
by creating these different types of patches, fire allows a greater
number of species to exist within a landscape.
Firefighting
==============
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.
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
infrared sensors 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
{{anchor|Fire management}}Management, prevention and protection systems
=========================================================================
Controlling a fire to optimize its size, shape, and intensity is
generally called 'fire management', and the more advanced forms of it,
as traditionally (and sometimes still) practiced by skilled cooks,
blacksmiths, ironmasters, and others, are highly skilled activities.
They include knowledge of which fuel to burn; how to arrange the fuel;
how to stoke the fire both in early phases and in maintenance phases;
how to modulate the heat, flame, and smoke as suited to the desired
application; how best to bank a fire to be revived later; how to
choose, design, or modify stoves, fireplaces, bakery ovens, or
industrial furnaces; and so on. Detailed expositions of fire
management are available in various books about blacksmithing, about
skilled camping or military scouting, and about domestic arts.
Wildfire prevention programs around the world may employ techniques
such as 'wildland fire use' and 'prescribed or controlled burns'.
'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 fire drills 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 building codes require passive fire protection and active fire
protection systems to minimize damage resulting from a fire. A 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.
Where fire prevention and fire protection have failed to prevent
damage, fire insurance can mitigate the financial impact.
In culture
======================================================================
Fire has been an importance element of human culture since the Lower
Paleolithic. Archaeological evidence demonstrates that fire worship
has been widely practiced since prehistory, with dedicated structures
found dating from at least the Chalcolithic period. The religion of
Zoroastrianism is closely linked to this practice. In some societies
fire was a deity, while others viewed it as the manifestation of the
divine. The fire in a hearth was perceived as symbolic of the Heavenly
Fire, and thus is considered a sacred component by fire worshipping
cultures. The origin of fire became a subject of mythology. In ancient
Greek culture, the Titan-god Prometheus was responsible for stealing
heavenly fire and gifting it to humanity.
The use of a pyre as a funerary 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 New Years 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.
See also
======================================================================
* 'The Chemical History of a Candle'
* Colored fire
* Deflagration
* Fire making
* Fire pit
* Fire whirl
* Flame test
* Life Safety Code
* List of fire deities
* List of fires
* List of light sources
* Piano burning
* Pyrokinesis
* Pyrolysis
* Pyromania
* Pyrophobia
Further reading
======================================================================
* Haung, Kai (2009). [
http://ecommons.txstate.edu/arp/287/ Population
and Building Factors That Impact Residential Fire Rates in Large U.S.
Cities. Applied Research Project] . Texas State University.
*
* Kosman, Admiel (January 13, 2011).
[
http://www.haaretz.com/weekend/magazine/sacred-fire-1.329892 "Sacred
fire"]. 'Haaretz'.
* Pyne, Stephen J. 'Fire : a brief history' (University of Washington
Press, 2001).
** Pyne, Stephen J. 'World fire : the culture of fire on earth' (1995)
[
https://archive.org/details/worldfireculture0000pyne online]
** Pyne, Stephen J. 'Tending fire : coping with America's wildland
fires' (2004)
[
https://archive.org/details/tendingfirecopin0000pyne_x6q9 online]
** Pyne, Stephen J. 'Awful splendour : a fire history of Canada'
(2007) [
https://archive.org/details/awfulsplendourfi0000pyne online]
** Pyne, Stephen J. 'Burning bush : a fire history of Australia'
(1991) [
https://archive.org/details/burningbushfireh0000pyne online]
** Pyne, Stephen J. 'Between Two Fires: A Fire History of Contemporary
America' (2015)
** Pyne, Stephen J. 'California: A Fire Survey' (2016)
* Safford, Hugh D., et al. "Fire ecology of the North American
Mediterranean-climate zone." in 'Fire ecology and management: Past,
present, and future of US forested ecosystems' (2021): 337-392. re
California and its neighbors
[
https://www.fs.usda.gov/research/treesearch/download/63841.pdf
online]
External links
======================================================================
* [
http://www.howstuffworks.com/Fire.htm How Fire Works] at
HowStuffWorks
* [
http://www.straightdope.com/columns/021122.html What exactly is
fire?] from The Straight Dope
* [
https://www.pbs.org/wgbh/nova/fire/onfire.html On Fire], an Adobe
Flash-based science tutorial from the 'NOVA' (TV series)
*
[
http://discovermagazine.com/2011/oct/20-things-you-didnt-know-about-fire
"20 Things You Didn't Know About... Fire"] from 'Discover' magazine
License
=========
All content on Gopherpedia comes from Wikipedia, and is licensed under CC-BY-SA
License URL:
http://creativecommons.org/licenses/by-sa/3.0/
Original Article:
http://en.wikipedia.org/wiki/Fire
