Smoke is a collection of particles and solid and liquid gases in the air emitted when the material is burning or pyrolysis, along with the quantity of air trapped or mixed into the mass. Generally these are unwanted by-products (including stoves, candles, oil lamps and fireplaces), but can also be used for pest control, communication (smoke signals), defensive and offensive abilities in military (smoke) screens) cooking, or smoking (tobacco, marijuana, etc.). Used in rituals where incense, sage, or resin is burned to produce odors for spiritual purposes. Smoke is sometimes used as a flavoring agent, and preservatives for various foods. Smoke is also a component of exhaust gases of internal combustion engines, especially diesel exhaust.
Inhalation smoke is the leading cause of death in indoor fire victims. Smoke kills with a combination of thermal damage, poisoning and lung irritation caused by carbon monoxide, hydrogen cyanide and other combustion products.
Smoke is the aerosol (or fog) of solid particles and liquid droplets that are close to the ideal size range for visible light noodle scattering. This effect has been likened to a three dimensional textured privacy glass - the smoke cloud does not block the image, but actually scrambles it.
Video Smoke
Chemical composition
The composition of the smoke depends on the nature of the burning fuel and the combustion conditions.
Fires with high oxygen availability burn at high temperatures and with a small amount of smoke produced; particles composed mostly of ash, or with large temperature differences, from condensed water aerosols. High temperatures also cause the production of nitrous oxide. The sulfur content produces sulfur dioxide, or in the case of incomplete combustion, of hydrogen sulfide. Carbon and hydrogen are almost completely oxidized to carbon dioxide and water. The burning flames with oxygen deprivation produce a much wider pallet of compounds, many of them toxic. The partial oxidation of carbon produces carbon monoxide, a nitrogen-containing material capable of producing hydrogen cyanide, ammonia, and nitrogen oxides. Hydrogen gas can be produced instead of water. Halogen content such as chlorine (eg in polyvinyl chloride or brominated flame retardant) may lead to the production of eg. hydrogen chloride, phosgene, dioxin, and chloromethane, bromomethane and other halokarbon. Hydrogen fluoride can be formed from fluorocarbons, whether fluoropolymers are subject to fire or halocarbon fire suppression agents. Phosphorus and antimony oxides and their reaction products can be formed from several fire retardant additives, increasing smoke toxicity and corrosivity. Polychlorinated biphenyls pyrolysis (PCB), for example from the burning of older transformer oils, and to lower levels also of other chlorine-containing materials, can produce 2,3,7,8-tetrachlorodibenzodioxin, strong carcinogens and other polychlorinated dibenzodioxins. Fluoropolymer Pyrolysis, eg. teflon, in the presence of oxygen carbonyl fluoride (which hydrolyzes easily into HF and CO 2 ); Other compounds may also form, eg. carbon tetrafluoride, hexafluoropropylene, and highly toxic perfluoroisobutene (PFIB).
Pyrolysis of combustible materials, particularly incomplete burning or smoldering without adequate oxygen supply, also result in the production of large quantities of hydrocarbons, both aliphatic (aromatic, ethane, ethylene, acetylene) and aromatics (benzene and its derivatives, aromatic polycyclic hydrocarbons eg benzo [ a] pyrene, studied as carcinogen, or retene), terpen. Heterocyclic compounds also exist. Heavier hydrocarbons can condense as tar; smoke with significant tar content of yellow to brown. The presence of smoke, soot, and/or oily precipitates such as brown during a fire indicates a potentially dangerous situation, since the atmosphere may be filled with flammable pyrolysis products concentrating above the upper flammable limit, and sudden airflow may cause flashover or backdraft..
The presence of sulfur can lead to the formation of eg. hydrogen sulfide, carbonyl sulfide, sulfur dioxide, carbon disulfide, and thiols; especially thiols tend to be adsorbed on the surface and produce a lingering odor even long after the fire. The partial oxidation of the released hydrocarbons produces a broad palette of other compounds: aldehydes (eg formaldehyde, acrolein, and furfural), ketones, alcohols (often aromatic, eg phenol, guaiacol, syringol, catechol, and cresols), carboxylic acids (formic). acids, acetic acid, etc.).
The particles seen in the smoke are most often composed of carbon (soot). Other particulates may be composed of tar droplets, or solid ash particles. The presence of metals in fuels produces metal oxide particles. Inorganic salt particles may also be formed, eg ammonium sulfate, ammonium nitrate, or sodium chloride. The inorganic salts on the surface of the soot particles can make them hydrophilic. Many organic compounds, usually aromatic hydrocarbons, can also be adsorbed on the surface of solid particles. Metal oxides can be present when fuels containing metals are burned, for example solid rocket fuel containing aluminum. The uranium projector that has run out after affecting the burn target, produces uranium oxide particles. Magnetic particles, spherules of iron ferrite oxide like magnets, present in coal smoke; the increase in their deposits after 1860 marked the beginning of the Industrial Revolution. (Magnetic iron oxide nanoparticles can also be produced in smoke from meteorites that burn in the atmosphere.) Magnetic remanents, recorded in iron oxide particles, show the strength of the Earth's magnetic field when cooled beyond their Curie temperatures; this can be used to distinguish magnetic particles of terrestrial and meteoric origins. Fly ash mainly consists of silica and calcium oxide. Cenospheres are present in the smoke from liquid hydrocarbon fuels. Metal particles produced by abrasion can be present in engine fumes. Particles of amorphous silica present in the smoke from silicon burning; A small part of the silicon nitride particles can form in a fire with insufficient oxygen. Silica particles have a size of about 10nm, clumped to 70-100 aggregates and then agglomerated into chains. Radioactive particles may be present due to traces of uranium, thorium, or other radionuclides in the fuel; heat particles can be present in case of fire during a nuclear accident (eg Chernobyl disaster) or nuclear war.
Smoke particulates, such as other aerosols, are categorized into three modes based on particle size:
- nuclei mode , with a geometric average radius of between 2.5-20 nm, possibly formed by the condensation of carbon moieties.
- accumulated modes , ranging from 75-250 nm and formed by coagulation of nuclear mode particles
- rough mode , with particles in the micrometer range
Most of the smoke material is mainly in coarse particles. Those who experience rapid dry rainfall, and smoke damage in areas further outdoors where fires occur because it is mainly mediated by smaller particles.
Aerosol particles outside the visible size are the initial indicators of material in the early stages of fire.
The burning of hydrogen-rich fuels produces water; this results in smoke containing moisture droplets. If no other source of color (nitrogen oxide, particulates...), such smoke is white and like a cloud.
The smoke emissions can contain trace elements characteristic. Vanadium is present in emissions from steam and oil refineries; the oil factory also issued some nickel. Burning coal produces emissions containing aluminum, arsenic, chromium, cobalt, copper, iron, mercury, selenium, and uranium.
Vanadium traces in high temperature combustion products form liquid vanadate droplets. It attacks the passivation layer on the metal and causes high temperature corrosion, which is of particular concern for internal combustion engines. Liquid sulfate and lead particulates also have such effects.
Some smoke components are characteristic of combustion sources. Guaiacol and its derivatives are lignin pyrolysis products and are characteristic of wood smoke; Other markers are syringols and derivatives, and other methoxy phenols. Retene, a coniferous pyrolysis product, is an indicator of forest fires. Levoglucosan is a cellulose pyrolysis product. Hardwood vs. softwood smoking differs in the ratio of guaiacols/syringols. Markers for vehicle disposal include polycyclic aromatic hydrocarbons, hops, steranes, and specific nitroarenes (eg 1-nitropirene). Hopanes and steranes ratios for carbon elements can be used to differentiate between gasoline and diesel fuel emissions.
Many compounds can be attributed to particulates; whether by being absorbed on its surface, or by dissolving in liquid droplets. Hydrogen chloride is well absorbed in soot particles.
Inert particles can be disrupted and enter into the smoke. Particular attention is asbestos particles.
Accumulated heat particles from radioactive fallout and bioaccumulation radioisotopes can be reintroduced into the atmosphere by forest fires and forest fires; this is a problem in eg. A zone of alienation containing contaminants from the Chernobyl disaster.
Polymers are a significant source of fumes. Aromatic side groups, e.g. in polystyrene, increasing smoke generation. The aromatic group integrated in the backbone of the polymer produces less smoke, possibly because of significant charcoal. Aliphatic polymers tend to produce less smoke, and non-self-extinguishing. However, the presence of additives can significantly increase smoke formation. Phosphorus-based and halogen-based fire retardants reduce smoke production. The higher cross link between the polymer chain has the same effect.
Invisible and invisible particles from burning
The naked eye detects particle sizes greater than 7 Âμm (micrometres). The visible particles emitted from the fire are called smoke. Invisible particles are commonly referred to as gases or fumes. This is best illustrated when baking bread in a toaster. As the bread heats up, the combustion products increase in size. The smoke that was originally produced was invisible but became noticeable if toast was burned.
The ionization-type smoke detector is technically a product of a combustion detector, not a smoke detector. The ionization-type smoke detector detects burning particles that are not visible to the naked eye. This explains why they are often wrongly alarmed from the smoke emitted from the heating heat elements from the toaster, before any visible smoke, but they may fail to activate at a low heat initial heat stage.
The smoke from a typical home fire contains hundreds of different chemicals and fumes. As a result, the damage caused by smoke can often exceed that caused by the actual heat of the fire. In addition to the physical damage caused by the smoke of fire - which manifests itself in the form of stains - is often more difficult to remove the smoke odor problem. Just as there are contractors who specialize in rebuilding/repairing homes that have been damaged by fire and smoke, the fabric restoration company specializes in recovering fabric that has been damaged in flames.
Maps Smoke
The smoke hazard
Smoke from oxygen-containing fires contains significant concentrations of flammable compounds. The smoke cloud, in contact with atmospheric oxygen, therefore has the potential to burn - either by another open fire in the area, or by its own temperature. This leads to effects such as backdraft and flashover. Inhaling smoke is also a danger of smoke that can cause serious injury and death.
Many smoke compounds from fire are very poisonous and/or irritating. The most dangerous is carbon monoxide that causes carbon monoxide poisoning, sometimes with the additive effects of hydrogen cyanide and phosgene. Inhaling the smoke can quickly lead to disability and loss of consciousness. Sulfur oxides, hydrogen chloride and hydrogen fluoride come in contact with water vapor to form sulfuric acid, hydrochloric and hydrofluoric, which are corrosive to the lungs and materials. When sleeping the nose does not feel the smoke or the brain, but the body will wake up if the lungs become covered with smoke and the brain will be stimulated and the person will wake up. This does not work if the person is unable or under the influence of drugs and/or alcohol.
Cigarette smoke is a major risk factor that can be modified for lung disease, heart disease, and many cancers. Smoke can also be a component of ambient air pollution due to the burning of coal in power plants, forest fires or other sources, although the concentration of pollutants in ambient air is usually much less than cigarette smoke. One day of PM2.5 exposure at a concentration of 880 μg/m3, as happened in Beijing, China, is equivalent to smoking one or two cigarettes in the case of heavy inhaled particulates. This analysis is complicated, however, by the fact that organic compounds present in various ambient particles may have higher carcinogenicity than the compounds in cigarette smoke particles. Secondhand smoke is a combination of sidestream and mainstream smoke emissions from burning tobacco products. This emission contains more than 50 carcinogenic chemicals. According to a recent Surgeon General report on this issue, "A brief exposure to secondhand smoke can cause blood platelets to become sticky, damage blood vessels, lower coronary flow reserves, and reduce cardiac variability, potentially increasing risk of heart attack." The American Cancer Society cites a list of "heart disease, lung infections, increased asthma attacks, middle ear infections, and low birth weight" as a consequence of smokers emissions.
Smoke can obscure visibility, blocking occupants coming out of the fire area. In fact, poor visibility due to smoke at the Cold Worcester Storage Warehouse in Worcester, Massachusetts is a good reason why trapped firefighters can not evacuate buildings on time. Because of the striking resemblance on every floor, thick smoke causes firefighters to be confused.
Smoke Corrosion
Smoke contains various chemicals, many of them aggressive in nature. Examples are hydrochloric and hydrobromic acids, which are produced from halogen-containing and fire-retardant plastics, fluoride acids released by pyrolysis of fluorocarbon fire suppressants, sulfuric acid from the burning of sulfur-containing materials, nitric acid from high temperature fires in which nitrous oxide gets formed, phosphoric acid and antimony compounds from flame retardants based on P and Sb, and many others. Such corrosion is not significant for structural materials, but fine structures, especially microelectronics, are severely affected. Corrosion of circuit board traces, aggressive penetration of aggressive chemicals through part casing, and other effects can cause rapid deterioration or parameter deterioration or even premature (and often delayed, long corrosion) failure of equipment to be smoked. Many smoke components are also electrically conductive; the precipitation of the conductive layer on the circuit may cause crosstalks and other defects of the operating parameters or even cause short circuits and total failure. Electrical contact may be affected by surface corrosion, and by sediment deposition and other conductive particles or non-conductive layers on or across contacts. The stored particles can affect optoelectronic performance by absorbing or diffusing light rays.
The smoke corrosivity produced by the material is characterized by a corrosion index ( CI ), which is defined as the level of material loss (angstrom/min) per gasification product (gram) per volume (m 3 ). This is measured by exposing the metallic strip to the stream of combustion products in the test tunnel. Polymers containing halogens and hydrogens (polyvinyl chloride, polyolefins with halogenated additives, etc.) have the highest CI as corrosive acids formed directly with water produced by combustion, only halogen-containing polymers (eg polytrafluoroethylene) have a lower CI as the formation of a limited acid in reaction with air humidity, and halogen-free material (polyolefin, wood) has the lowest CI. However, some halogen-free materials can also release large amounts of corrosive products.
Damage caused by smoke in electronic equipment can be much wider than the fire itself. Cable fires are of particular concern; low smoke halogen zero material is preferred for cable insulation.
When smoke is in contact with the surface of any substance or structure, the chemicals contained therein will be transferred there. The corrosive nature of the chemical causes the substance or structure to decompose at a rapid rate. Certain materials or structures absorb this chemical, that is why clothing, unclosed surfaces, drinkable water, pipes, wood, etc., are replaced in many cases of structural fires.
Measurement
At the beginning of the fifteenth century, Leonardo da Vinci commented at length about the difficulty of assessing smoke, and distinguished between black smoke (carbonaceous particles) and 'smoke' whites which were not smoke at all but only a harmless particulate water suspension.
Smoke from a heater is generally measured in one of the following ways:
In-line capture. The smoke sample is only aspirated through the filter weighed before and after the test and the smoke mass found. This is the simplest and perhaps most accurate method, but can only be used where the smoke concentration is small, since the filter can quickly become obstructed.
The ASTM smoke pump is a simple and widely used in-line fishing method in which the measured smoke volume is drawn through the filter paper and the dark point formed compared to the standard.
Filter/dilution tunnel. The smoke sample is taken through air-dissolved tube, the resulting air/air mixture is then drawn through the filter and weighed. This is an internationally recognized method of measuring smoke from burning.
Electrostatic precipitation. Smoke is passed through various metal tubes containing hanging wires. The (large) electrical potential is applied across the tube and cable so that the smoke particles become filled and drawn to the side of the tube. This method can be over-read by capturing a harmless condensate, or less read because of the insulating effects of the smoke. However, the method required to assess the volume of smoke is too great to be forced through a filter, ie from bituminous coal.
The Ringelmann scale. Smoke color size. Invented by Professor Maximilian Ringelmann in Paris in 1888, is basically a card with black, white and gray-colored boxes that are lifted and gray smoke comparison comparisons. Depending heavily on the light conditions and skill of the observer, he allocates the gray number from 0 (white) to 5 (black) which has only a passing relationship with the actual quantity of smoke. Nevertheless, the simplicity of the Ringelmann scale means it has been adopted as a standard in many countries.
Optical scattering. The rays are passed through the smoke. The light detector is located at an angle to the light source, usually at 90 °, so it only accepts reflected light from the passing particles. Measurements are made from received light which will be higher because the concentration of smoke particles becomes higher.
Optical obscuration. Rays are passed through the smoke and the opposite detectors measure the light. The more smoke particles present between the two, the less light it will measure.
Combined optical methods. There are various proprietary optical smoke measurement devices such as 'nephelometer' or 'aethalometer' using several different optical methods, including more than one wavelength of light, within a single instrument and applying the algorithm to provide a good smoke forecast. It has been claimed that these devices can distinguish the types of smoke and thus their possible source can be inferred, although this is disputed.
Conclusions from carbon monoxide. Smoke is unburnt fuel, carbon monoxide is unburnt carbon, therefore it has long been assumed that the measurement of CO in the flue gas (a cheap, simple and very accurate procedure) will give a good indication of the smoke level. Indeed, some jurisdictions use CO measurements as a basis for smoke control. But it is far from clear how accurate the correspondence is.
Medical smoke
Throughout recorded history, humans have used herbal medicine to cure diseases. A statue of Persepolis shows Darius the Great (522-486 BC), the king of Persia, with two censors ahead of him to burn the album Peganum harmala and/or Sandalwood Santalum, which is believed to protect the king from evil and disease. More than 300 species of plants on five continents are used in the form of smoke for various diseases. As a method of drug delivery, smoking is important because it is a method of extracting particles containing active agents that are simple, inexpensive, but very effective. More importantly, producing smoke reduces particle size to a microscopic scale thus increasing the absorption of its active chemical principle.
See also
- Ã, "Smoke". EncyclopÃÆ'Â|dia Britannica . 25 (issue 11). 1911.
References
External links
- Wood burner Site
- Spill new light on wood smoke
Source of the article : Wikipedia
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