Editing Smoke (section)

==Chemical composition==
[[File:Smoke chemical composition.jpg|thumb|Chemical composition distribution of [[volatile organic compound]]s released in smoke from a variety of solid [[fuel]]s<ref name="Stewart et al 2021">{{cite journal |last1=Stewart |first1=Gareth J. |last2=Acton |first2=W. Joe F. |last3=Nelson |first3=Beth S. |last4=Vaughan |first4=Adam R. |last5=Hopkins |first5=James R. |last6=Arya |first6=Rahul |last7=Mondal |first7=Arnab |last8=Jangirh |first8=Ritu |last9=Ahlawat |first9=Sakshi |last10=Yadav |first10=Lokesh |last11=Sharma |first11=Sudhir K. |last12=Dunmore |first12=Rachel E. |last13=Yunus |first13=Siti S. M. |last14=Hewitt |first14=C. Nicholas |last15=Nemitz |first15=Eiko |last16=Mullinger |first16=Neil |last17=Gadi |first17=Ranu |last18=Sahu |first18=Lokesh K. |last19=Tripathi |first19=Nidhi |last20=Rickard |first20=Andrew R. |last21=Lee |first21=James D. |last22=Mandal |first22=Tuhin K. |last23=Hamilton |first23=Jacqueline F. |title=Emissions of non-methane volatile organic compounds from combustion of domestic fuels in Delhi, India |journal=Atmospheric Chemistry and Physics |date=18 February 2021 |volume=21 |issue=4 |pages=2383–2406 |doi=10.5194/acp-21-2383-2021 |bibcode=2021ACP....21.2383S |doi-access=free }}</ref>]]
The composition of smoke depends on the nature of the burning fuel and the conditions of combustion. Fires with high availability of oxygen burn at a high temperature and with a small amount of smoke produced; the particles are mostly composed of [[ash]], or with large temperature differences, of condensed aerosol of water. High temperature also leads to production of [[nitrogen oxide]]s.<ref>{{cite book |last=Lee |first=C.C. |date=1 January 2005 |title=Environmental Engineering Dictionary |url=https://books.google.com/books?id=f1lnQwrvOSEC&q=high+burning+temperature+nitrogen+oxide&pg=PA528 |publisher=Government Institutes |page=528 |isbn=978-0-86587-848-8 |access-date=20 October 2020 |archive-date=3 April 2023 |archive-url=https://web.archive.org/web/20230403234019/https://books.google.com/books?id=f1lnQwrvOSEC&q=high+burning+temperature+nitrogen+oxide&pg=PA528 |url-status=live }}</ref> Sulfur content yields [[sulfur dioxide]], or in case of incomplete combustion, [[hydrogen sulfide]].<ref>{{cite book |last=Carlone |first=Nancy |year=2009 |title=Nancy Caroline's Emergency Care in the Streets, Canadian Edition |url=https://books.google.com/books?id=Tw7SF2LyOYoC&q=lack+of+oxygen+sulfur+dioxide+incomplete+combustion+hydrogen+sulfide&pg=SA20-PA27 |location=[[Burlington, Massachusetts]] |publisher=[[Jones & Bartlett Learning]] |pages=20–28 |isbn=978-1-284-05384-5 |access-date=20 October 2020 |archive-date=3 April 2023 |archive-url=https://web.archive.org/web/20230403233722/https://books.google.com/books?id=Tw7SF2LyOYoC&q=lack+of+oxygen+sulfur+dioxide+incomplete+combustion+hydrogen+sulfide&pg=SA20-PA27 |url-status=live }}</ref> Carbon and hydrogen are almost completely oxidized to [[carbon dioxide]] and water.<ref name="botany">{{cite book |last=Mauseth |first=James D. |year=1991 |title=Botany: An Introduction to Plant Biology |url=https://books.google.com/books?id=0BGEs95p5EsC&q=Carbon+and+hydrogen+almost+completely+oxidized+to+carbon+dioxide+and+water&pg=PA234 |location=[[Burlington, Massachusetts]] |publisher=[[Jones & Bartlett Learning]] |page=234 |isbn=978-0-03-093893-1 |access-date=20 October 2020 |archive-date=4 April 2023 |archive-url=https://web.archive.org/web/20230404030206/https://books.google.com/books?id=0BGEs95p5EsC&q=Carbon+and+hydrogen+almost+completely+oxidized+to+carbon+dioxide+and+water&pg=PA234 |url-status=live }}</ref> Fires burning with lack of oxygen produce a significantly wider palette of compounds, many of them toxic.<ref name="botany"/> [[Partial oxidation]] of carbon produces [[carbon monoxide]], while nitrogen-containing materials can yield [[hydrogen cyanide]], [[ammonia]], and nitrogen oxides.<ref name="metrics">{{cite book |last1=Reuter |first1=M.A. |last2=Boin |first2=U.M.J. |last3=Schaik |first3=A. van |last4=Verhoef |first4=E. |last5=Heiskanen |first5=K. |last6=Yang |first6=Yongxiang |last7=Georgalli |first7=G. |date=2 November 2005 |title=The Metrics of Material and Metal Ecology |url=https://books.google.com/books?id=IyCz1MoXGBsC&q=oxidation+of+carbon+produces+carbon+monoxide&pg=PA145 |location=Amsterdam |publisher=[[Elsevier]] |isbn=978-0-08-045792-5 |access-date=20 October 2020 |archive-date=3 April 2023 |archive-url=https://web.archive.org/web/20230403234021/https://books.google.com/books?id=IyCz1MoXGBsC&q=oxidation+of+carbon+produces+carbon+monoxide&pg=PA145 |url-status=live }}</ref> [[Hydrogen]] gas can be produced instead of water.<ref name="metrics"/> Contents of [[halogens]] such as [[chlorine]] (e.g. in [[polyvinyl chloride]] or [[brominated flame retardant]]s) may lead to the production of [[hydrogen chloride]], [[phosgene]], [[Polychlorinated dibenzodioxins|dioxin]], and [[chloromethane]], [[bromomethane]] and other [[halocarbon]]s.<ref name="metrics"/><ref name="plasrub">{{cite book |last=Fardell |first=P.J. |date=1 January 1993 |title=Toxicity of Plastics and Rubber in Fire |url=https://books.google.com/books?id=lmhD_QKpTTkC&q=brominated+flame+retardant+phosgene+hydrogen+chloride&pg=PA67 |publisher=[[iSmithers Rapra Publishing]] |isbn=978-1-85957-001-2 |access-date=20 October 2020 |archive-date=3 April 2023 |archive-url=https://web.archive.org/web/20230403234020/https://books.google.com/books?id=lmhD_QKpTTkC&q=brominated+flame+retardant+phosgene+hydrogen+chloride&pg=PA67 |url-status=live }}</ref> [[Hydrogen fluoride]] can be formed from [[fluorocarbon]]s, whether [[fluoropolymer]]s subjected to fire or halocarbon [[fire suppression agent]]s. [[Phosphorus]] and [[antimony]] oxides and their reaction products can be formed from some [[fire retardant]] additives, increasing smoke toxicity and corrosivity.<ref name="plasrub"/> [[Pyrolysis]] of [[polychlorinated biphenyl]]s (PCB), e.g. from burning older [[transformer oil]], and to lower degree also of other chlorine-containing materials, can produce [[2,3,7,8-Tetrachlorodibenzodioxin|2,3,7,8-tetrachlorodibenzodioxin]], a potent [[carcinogen]], and other [[polychlorinated dibenzodioxins]].<ref name="plasrub"/> Pyrolysis of fluoropolymers, e.g. [[teflon]], in presence of oxygen yields [[carbonyl fluoride]] (which hydrolyzes readily to HF and CO<sub>2</sub>); other compounds may be formed as well, e.g. [[carbon tetrafluoride]], [[hexafluoropropylene]], and highly toxic [[perfluoroisobutene]] (PFIB).<ref name="flamsmokcable"/>

[[File:Diesel-smoke.jpg|thumb|Emission of soot in the fumes of a large [[diesel engine|diesel]] truck, without particle filters]]

Pyrolysis of burning material, especially [[incomplete combustion]] or [[smoldering]] without adequate oxygen supply, also results in production of a large amount of [[hydrocarbons]], both [[aliphatic]] ([[methane]], [[ethane]], [[ethylene]], [[acetylene]]) and [[aromatic hydrocarbon|aromatic]] ([[benzene]] and its derivates, [[polycyclic aromatic hydrocarbon]]s; e.g. [[benzopyrene|benzo[a]pyrene]], studied as a carcinogen, or [[retene]]), [[terpene]]s.<ref>{{cite book |last=Moldoveanu |first=S.C. |date=11 November 1998 |title=Analytical Pyrolysis of Natural Organic Polymers |url=https://books.google.com/books?id=r4TMd5hC75MC&q=chemical+composition+of+smoke+pyrolosis |publisher=Elsevier |pages=152, 428 |isbn=978-0-444-82203-1 |access-date=20 October 2020 |archive-date=3 April 2023 |archive-url=https://web.archive.org/web/20230403233721/https://books.google.com/books?id=r4TMd5hC75MC&q=chemical+composition+of+smoke+pyrolosis |url-status=live }}</ref> It also results in the emission of a range of smaller oxygenated [[volatile organic compounds]] ([[methanol]], [[acetic acid]], [[Hydroxyacetone|hydroxy acetone]], [[methyl acetate]] and [[ethyl formate]]) which are formed as combustion by products as well as less volatile oxygenated organic species such as phenolics, [[furan]]s and [[furanone]]s.<ref name="Stewart et al 2021"/> [[Heterocyclic compound]]s may be also present.<ref>{{cite book |last=Moldoveanu |first=Serban |date=16 September 2009 |title=Pyrolysis of Organic Molecules: Applications to Health and Environmental Issues |url=https://books.google.com/books?id=lg2r9BDlbM8C&q=Heterocyclic+compounds+pyrolysis |publisher=Elsevier |page=643 |isbn=978-0-444-53113-1 |access-date=20 October 2020 |archive-date=3 April 2023 |archive-url=https://web.archive.org/web/20230403234019/https://books.google.com/books?id=lg2r9BDlbM8C&q=Heterocyclic+compounds+pyrolysis |url-status=live }}</ref> Heavier hydrocarbons may condense as [[tar]]; smoke with significant tar content is yellow to brown.<ref>{{cite book |author=Staff writer<!--no by-line--> |year=1892 |title=A dictionary of the coal tar colours |url=https://books.google.com/books?id=lY45AQAAIAAJ&q=significant+tar+yellow+to+brown |publisher=Heywood and Co. |page=8 |isbn=978-1-4097-0169-9 |access-date=20 October 2020 |archive-date=4 April 2023 |archive-url=https://web.archive.org/web/20230404030207/https://books.google.com/books?id=lY45AQAAIAAJ&q=significant+tar+yellow+to+brown |url-status=live }}</ref> Combustion of solid fuels can result in the emission of many hundreds to thousands of lower volatility organic compounds in the aerosol phase.<ref>{{cite journal |last1=Stewart |first1=Gareth J. |last2=Nelson |first2=Beth S. |last3=Acton |first3=W. Joe F. |last4=Vaughan |first4=Adam R. |last5=Farren |first5=Naomi J. |last6=Hopkins |first6=James R. |last7=Ward |first7=Martyn W. |last8=Swift |first8=Stefan J. |last9=Arya |first9=Rahul |last10=Mondal |first10=Arnab |last11=Jangirh |first11=Ritu |last12=Ahlawat |first12=Sakshi |last13=Yadav |first13=Lokesh |last14=Sharma |first14=Sudhir K. |last15=Yunus |first15=Siti S. M. |last16=Hewitt |first16=C. Nicholas |last17=Nemitz |first17=Eiko |last18=Mullinger |first18=Neil |last19=Gadi |first19=Ranu |last20=Sahu |first20=Lokesh K. |last21=Tripathi |first21=Nidhi |last22=Rickard |first22=Andrew R. |last23=Lee |first23=James D. |last24=Mandal |first24=Tuhin K. |last25=Hamilton |first25=Jacqueline F. |title=Emissions of intermediate-volatility and semi-volatile organic compounds from domestic fuels used in Delhi, India |journal=Atmospheric Chemistry and Physics |date=18 February 2021 |volume=21 |issue=4 |pages=2407–2426 |doi=10.5194/acp-21-2407-2021 |bibcode=2021ACP....21.2407S |doi-access=free }}</ref> Presence of such smoke, soot, and/or brown oily deposits during a fire indicates a possible hazardous situation, as the atmosphere may be saturated with combustible pyrolysis products with concentration above the upper [[flammability limit]], and sudden inrush of air can cause [[flashover]] or [[backdraft]].<ref>{{cite book |last=Fire |first=Frank L. |year=2009 |title=The Common Sense Approach to Hazardous Materials |url=https://books.google.com/books?id=6AGGHbXVpSsC&q=pyrolysis+flashover+backdraft |publisher=Fire Engineering Books |page=129 |isbn=978-0-912212-11-1 |access-date=20 October 2020 |archive-date=3 April 2023 |archive-url=https://web.archive.org/web/20230403234022/https://books.google.com/books?id=6AGGHbXVpSsC&q=pyrolysis+flashover+backdraft |url-status=live }}</ref>

Presence of sulfur can lead to formation of gases like hydrogen sulfide, [[carbonyl sulfide]], sulfur dioxide, [[carbon disulfide]], and [[thiol]]s; especially thiols tend to get adsorbed on surfaces and produce a lingering odor even long after the fire. Partial oxidation of the released hydrocarbons yields in a wide palette of other compounds: [[aldehyde]]s (e.g. [[formaldehyde]], [[acrolein]], and [[furfural]]), ketones, [[alcohols]] (often aromatic, e.g. [[phenol]], [[guaiacol]], [[syringol]], [[catechol]], and [[cresol]]s), [[carboxylic acid]]s ([[formic acid]], [[acetic acid]], etc.).{{citation needed|date=January 2022}}

The visible [[Atmospheric particulate matter|particulate matter]] in such smokes is most commonly composed of [[carbon]] ([[soot]]). Other particulates may be composed of drops of condensed tar, or solid particles of ash. The presence of metals in the fuel yields particles of metal [[oxide]]s. Particles of inorganic [[salt (chemistry)|salts]] may also be formed, e.g. [[ammonium sulfate]], [[ammonium nitrate]], or [[sodium chloride]]. Inorganic salts present on the surface of the soot particles may make them [[hydrophilic]]. Many organic compounds, typically the [[aromatic hydrocarbon]]s, may be also [[adsorb]]ed on the surface of the solid particles. Metal oxides can be present when metal-containing fuels are burned, e.g. [[solid rocket]] fuels containing [[aluminium]]. [[Depleted uranium]] projectiles after impacting the target ignite, producing particles of [[uranium oxide]]s. [[Magnetic]] particles, spherules of [[magnetite]]-like [[ferrous ferric oxide]], are present in coal smoke; their increase in deposits after 1860 marks the beginning of the Industrial Revolution.<ref>{{cite journal |last1=Oldfield |first1=F. |last2=Tolonen |first2=K. |last3=Thompson |first3=R. |jstor=4312673 |title=History of Particulate Atmospheric Pollution from Magnetic Measurements in Dated Finnish Peat Profiles |name-list-style=amp |journal=Ambio |volume=10 |issue=4 |year=1981 |page=185}}</ref> (Magnetic iron oxide [[nanoparticle]]s can be also produced in the smoke from [[meteorite]]s burning in the atmosphere.)<ref>{{cite journal |last1=Lanci |first1=L. |last2=Kent |first2=D. V. |title=Meteoric smoke fallout revealed by superparamagnetism in Greenland ice |journal=Geophysical Research Letters |date=2006 |volume=33 |issue=13 |pages=L13308 |doi=10.1029/2006GL026480 |bibcode=2006GeoRL..3313308L |doi-access=free }}</ref> Magnetic [[remanence]], [[paleomagnetism|recorded]] in the iron oxide particles, indicates the strength of Earth's magnetic field when they were cooled beyond their [[Curie temperature]]; this can be used to distinguish magnetic particles of terrestrial and meteoric origin.<ref>{{cite journal |last1=Suavet |first1=C. |last2=Gattacceca |first2=J. |last3=Rochette |first3=P. |last4=Perchiazzi |first4=N. |last5=Folco |first5=L. |last6=Duprat |first6=J. |last7=Harvey |first7=R. P. |title=Magnetic properties of micrometeorites |journal=Journal of Geophysical Research |date=4 April 2009 |volume=114 |issue=B4 |pages=B04102 |doi=10.1029/2008JB005831 |bibcode=2009JGRB..114.4102S |url=http://hal.in2p3.fr/in2p3-00684671/file/2008JB005831.pdf |access-date=25 January 2022 |archive-date=5 February 2022 |archive-url=https://web.archive.org/web/20220205105731/http://hal.in2p3.fr/in2p3-00684671/file/2008JB005831.pdf |url-status=live }}</ref> [[Fly ash]] is composed mainly of [[silica]] and [[calcium oxide]]. [[Cenosphere]]s are present in smoke from liquid hydrocarbon fuels. Minute metal particles produced by [[abrasion (mechanical)|abrasion]] can be present in engine smokes. [[Amorphous silica]] particles are present in smokes from burning [[silicone]]s; small proportion of [[silicon nitride]] particles can be formed in fires with insufficient oxygen. The silica particles have about 10&nbsp;nm size, clumped to 70–100&nbsp;nm aggregates and further agglomerated to chains.<ref name="flamsmokcable">{{cite book |author=National Research Council (U.S.). Task Force on Flammability, Smoke, Toxicity and Corrosive Gases of Electric Cable Materials |title=Flammability, smoke, toxicity, and corrosive gases of electric cable materials: report of the Task Force on Flammability, Smoke, Toxicity, and Corrosive Gases of Electric Cable Materials, National Materials Advisory Board, Commission on Sociotechnical Systems, National Research Council |url=https://books.google.com/books?id=6WYrAAAAYAAJ&pg=PA107|year=1978 |publisher=National Academies |pages=107– |id=NAP:15488}}</ref> Radioactive particles may be present due to traces of [[uranium]], [[thorium]], or other [[radionuclide]]s in the fuel; [[hot particle]]s can be present in case of fires during [[nuclear accident]]s (e.g. [[Chernobyl disaster]]) or [[nuclear war]].

Smoke particulates, like other aerosols, are categorized into three modes based on particle size:
* '''nuclei mode''', with [[geometric mean]] radius between 2.5 and 20&nbsp;nm, likely forming by condensation of carbon [[Moiety (chemistry)|moieties]].
* '''[[accumulation mode]]''', ranging between 75 and 250&nbsp;nm and formed by coagulation of nuclei mode particles
* '''[[coarse mode]]''', with particles in micrometer range
Most of the smoke material is primarily in coarse particles. Those undergo rapid [[dry precipitation]], and the smoke damage in more distant areas outside of the room where the fire occurs is therefore primarily mediated by the smaller particles.<ref name="physproppoly"/>

Aerosol of particles beyond visible size is an early indicator of materials in a preignition stage of a fire.<ref name="flamsmokcable"/>

Burning of hydrogen-rich fuel produces [[water vapor]]; this results in smoke containing droplets of water. In absence of other color sources (nitrogen oxides, particulates...), such smoke is white and [[cloud]]-like.

Smoke emissions may contain characteristic trace elements. [[Vanadium]] is present in emissions from [[oil]] fired power plants and [[Oil refinery|refineries]]; oil plants also emit some [[nickel]]. Coal combustion [[Fossil fuel power plant#Environmental impacts|produces emissions]] containing [[aluminium]], [[arsenic]], [[chromium]], [[cobalt]], [[copper]], [[iron]], [[mercury (element)|mercury]], [[selenium]], and [[uranium]].

Traces of vanadium in high-temperature combustion products form droplets of molten [[vanadate]]s. These attack the [[Passivation (chemistry)|passivation layer]]s on metals and cause [[high temperature corrosion]], which is a concern especially for [[internal combustion engine]]s. Molten [[sulfate]] and [[lead]] particulates also have such effect.

Some components of smoke are characteristic of the combustion source. [[Guaiacol]] and its derivatives are products of pyrolysis of [[lignin]] and are characteristic of [[wood]] smoke; other markers are [[syringol]] and derivates, and other [[methoxy]] [[phenol]]s. [[Retene]], a product of pyrolysis of [[conifer]] trees, is an indicator of [[forest fire]]s. [[Levoglucosan]] is a pyrolysis product of [[cellulose]]. [[Hardwood]] vs [[softwood]] smokes differ in the ratio of guaiacols/syringols. Markers for vehicle exhaust include [[polycyclic aromatic hydrocarbon]]s, [[hopane]]s, [[sterane]]s, and specific nitroarenes (e.g. [[1-nitropyrene]]). The ratio of hopanes and steranes to elemental carbon can be used to distinguish between emissions of gasoline and diesel engines.<ref>{{cite web |url=http://www.wrapair.org/APACE/SPECIATION/Synopsis_topic7.htm |title=Organic Speciation International Workshop Synthesis_topic7 |publisher=Wrapair.org |access-date=19 February 2010 |archive-date=26 July 2017 |archive-url=https://web.archive.org/web/20170726052050/https://www.wrapair.org/APACE/SPECIATION/Synopsis_topic7.htm |url-status=live }}</ref>

Many compounds can be associated with particulates; whether by being [[adsorption|adsorbed]] on their surfaces, or by being dissolved in liquid droplets. Hydrogen chloride is well absorbed in the soot particles.<ref name="physproppoly"/>

Inert particulate matter can be disturbed and entrained into the smoke. Of particular concern are particles of [[asbestos]].

Deposited [[hot particle]]s of [[radioactive fallout]] and bioaccumulated radioisotopes can be reintroduced into the atmosphere by [[wildfire]]s and [[forest fire]]s; this is a concern in e.g. the [[Zone of alienation]] containing contaminants from the [[Chernobyl disaster]].

Polymers are a significant source of smoke. Aromatic [[side group]]s, e.g. in [[polystyrene]], enhance generation of smoke. Aromatic groups integrated in the polymer backbone produce less smoke, likely due to significant [[charring]]. Aliphatic polymers tend to generate the least smoke, and are non-self-extinguishing. However presence of additives can significantly increase smoke formation. Phosphorus-based and halogen-based [[flame retardant]]s decrease production of smoke. Higher degree of [[cross-link]]ing between the polymer chains has such effect too.<ref>{{cite book |last1=Krevelen |first1=D.W. van |last2=Nijenhuis |first2=Klaas te |page=864 |url=https://books.google.com/books?id=bzRKwjZeQ2kC&pg=PA864 |title=Properties of Polymers: Their Correlation with Chemical Structure; Their Numerical Estimation and Prediction from Additive Group Contributions |publisher=Elsevier |year=2009 |isbn=978-0-08-054819-7 |access-date=25 September 2016 |archive-date=14 July 2020 |archive-url=https://web.archive.org/web/20200714131333/https://books.google.com/books?id=bzRKwjZeQ2kC&pg=PA864 |url-status=live }}</ref>

===Visible and invisible particles of combustion===
{{unreferenced section|date=January 2022}}
[[File:Wildfiretopanga.jpg|thumb|Smoke from a [[wildfire]]]]
[[File:Muizenberg Mountian Fires in Cape Town of 2015.jpg|thumbnail|Smoke rising up from the smoldering remains of a recently extingished mountain fire in South Africa]]
The [[naked eye]] detects particle sizes greater than 7&nbsp;μm ([[micrometres]]).<ref>{{Cite web |title=How small can the naked eye see? |url=https://www.sciencefocus.com/the-human-body/how-small-can-the-naked-eye-see |access-date=2024-05-25 |website=www.sciencefocus.com |language=en}}</ref> [[Visibility|Visible]] particles emitted from a fire are referred to as smoke. [[Invisibility|Invisible]] particles are generally referred to as gas or fumes. This is best illustrated when [[Toast (food)|toast]]ing bread in a toaster. As the bread heats up, the products of combustion increase in size. The fumes initially produced are invisible but become visible if the toast is burnt.

An [[ionization chamber]] type [[smoke detector]] is technically a product of combustion detector, not a smoke detector. Ionization chamber type smoke detectors detect particles of combustion that are invisible to the naked eye. This explains why they may frequently [[false alarm]] from the fumes emitted from the red-hot heating elements of a toaster, before the presence of visible smoke, yet they may fail to activate in the early, low-heat [[smoldering]] stage of a fire.

Smoke from a typical house fire contains hundreds of different chemicals and fumes. As a result, the damage caused by the smoke can often exceed that caused by the actual heat of the fire. In addition to the physical damage caused by the smoke of a [[fire]] – which manifests itself in the form of stains – is the often even harder to eliminate problem of a smoky odor. Just as there are contractors that specialize in rebuilding/repairing homes that have been damaged by fire and smoke, [[fabric restoration]] companies specialize in restoring fabrics that have been damaged in a fire.