
Smoke is a suspension of airborne
particulates and
gases emitted when a material undergoes
combustion or
pyrolysis, together with the quantity of air that is
entrained or otherwise mixed into the mass. It is commonly an unwanted
by-product
A by-product or byproduct is a secondary product derived from a production process, manufacturing process or chemical reaction; it is not the primary product or service being produced.
A by-product can be useful and marketable or it can be consid ...
of fires (including
stoves,
candles,
internal combustion engines,
oil lamps, and
fireplaces), but may also be used for
pest control (
fumigation
Fumigation is a method of pest control or the removal of harmful micro-organisms by completely filling an area with gaseous pesticides—or fumigants—to suffocate or poison the pests within. It is used to control pests in buildings (s ...
), communication (
smoke signal
The smoke signal is one of the oldest forms of long-distance communication. It is a form of visual communication used over a long distance. In general smoke signals are used to transmit news, signal danger, or to gather people to a common area ...
s), defensive and offensive capabilities in the military (
smoke screen),
cooking
Cooking, cookery, or culinary arts is the art, science and craft of using heat to Outline of food preparation, prepare food for consumption. Cooking techniques and ingredients vary widely, from grilling food over an open fire to using electric ...
, or
smoking
Smoking is a practice in which a substance is burned and the resulting smoke is typically breathed in to be tasted and absorbed into the bloodstream. Most commonly, the substance used is the dried leaves of the tobacco plant, which have bee ...
(
tobacco,
cannabis, etc.). It is used in rituals where
incense,
sage
Sage or SAGE may refer to:
Plants
* ''Salvia officinalis'', common sage, a small evergreen subshrub used as a culinary herb
** Lamiaceae, a family of flowering plants commonly known as the mint or deadnettle or sage family
** ''Salvia'', a large ...
, or
resin is burned to produce a smell for spiritual or magical purposes. It can also be a flavoring agent and preservative.
Smoke inhalation is the primary cause of death in victims of indoor
fires. The smoke kills by a combination of thermal damage,
poison
Poison is a chemical substance that has a detrimental effect to life. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figuratively, with a broa ...
ing and
pulmonary irritation caused by
carbon monoxide,
hydrogen cyanide
Hydrogen cyanide, sometimes called prussic acid, is a chemical compound with the formula HCN and structure . It is a colorless, extremely poisonous, and flammable liquid that boils slightly above room temperature, at . HCN is produced on an ...
and other combustion products.
Smoke is an
aerosol
An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...
(or
mist
Mist is a phenomenon caused by small droplets of water suspended in the cold air, usually by condensation. Physically, it is an example of a dispersion. It is most commonly seen where water vapor in warm, moist air meets sudden cooling, such a ...
) of solid particles and liquid droplets that are close to the ideal range of sizes for
Mie scattering of
visible light.
Chemical composition
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
Ash or ashes are the solid remnants of fires. Specifically, ''ash'' refers to all non-aqueous, non- gaseous residues that remain after something burns. In analytical chemistry, to analyse the mineral and metal content of chemical samples, ash ...
, or with large temperature differences, of condensed aerosol of water. High temperature also leads to production of
nitrogen oxide Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:
Charge-neutral
*Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide
*Nitrogen dioxide (), nitrogen(IV) oxide
* Nitrogen trioxide (), or n ...
s. Sulfur content yields
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
, or in case of incomplete combustion,
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
. Carbon and hydrogen are almost completely oxidized to
carbon dioxide and water.
Fires burning with lack of oxygen produce a significantly wider palette of compounds, many of them toxic.
Partial oxidation of carbon produces
carbon monoxide, while nitrogen-containing materials can yield
hydrogen cyanide
Hydrogen cyanide, sometimes called prussic acid, is a chemical compound with the formula HCN and structure . It is a colorless, extremely poisonous, and flammable liquid that boils slightly above room temperature, at . HCN is produced on an ...
,
ammonia, and nitrogen oxides.
Hydrogen gas can be produced instead of water.
Contents of
halogens such as
chlorine (e.g. in
polyvinyl chloride or
brominated flame retardants) may lead to the production of
hydrogen chloride,
phosgene
Phosgene is the organic chemical compound with the formula COCl2. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. Phosgene is a valued and important industrial building block, espe ...
,
dioxin
Dioxin may refer to:
* 1,2-Dioxin or 1,4-Dioxin, two unsaturated heterocyclic 6-membered rings where two carbon atoms have been replaced by oxygen atoms, giving the molecular formula C4H4O2
*Dibenzo-1,4-dioxin, the parent compound also known as ...
, and
chloromethane,
bromomethane and other
halocarbon
Halocarbon compounds are chemicals in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms (fluorine, chlorine, bromine or iodine – ) resulting in the formation of organofluorine compounds, organochlori ...
s.
Hydrogen fluoride
Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock i ...
can be formed from
fluorocarbon
Fluorocarbons are chemical compounds with carbon-fluorine bonds. Compounds that contain many C-F bonds often has distinctive properties, e.g., enhanced stability, volatility, and hydrophobicity. Fluorocarbons and their derivatives are commerci ...
s, whether
fluoropolymer
A fluoropolymer is a fluorocarbon-based polymer with multiple carbon–fluorine bonds. It is characterized by a high resistance to solvents, acids, and bases. The best known fluoropolymer is polytetrafluoroethylene under the brand name "Teflon ...
s subjected to fire or halocarbon
fire suppression agent
A fire retardant is a substance that is used to slow down or stop the spread of fire or reduce its intensity. This is commonly accomplished by chemical reactions that reduce the flammability of fuels or delay their combustion. Fire retardants m ...
s.
Phosphorus and
antimony oxides and their reaction products can be formed from some
fire retardant
A fire retardant is a substance that is used to slow down or stop the spread of fire or reduce its intensity. This is commonly accomplished by chemical reactions that reduce the flammability of fuels or delay their combustion. Fire retardants m ...
additives, increasing smoke toxicity and corrosivity.
Pyrolysis of
polychlorinated biphenyls (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-Tetrachlorodibenzo-''p-''dioxin (TCDD) is a polychlorinated dibenzo''-p-''dioxin (sometimes shortened, though inaccurately, to simply 'dioxin')Tuomisto, Jouko (2019) Dioxins and dioxin-like compounds: toxicity in humans and animals, s ...
, a potent
carcinogen, and other
polychlorinated dibenzodioxins
Polychlorinated dibenzodioxins (PCDDs), or simply dioxins, are a group of long-lived polyhalogenated compound, polyhalogenated organic compounds that are primarily anthropogenic, and contribute toxic, Persistent organic pollutant, persistent org ...
.
Pyrolysis of fluoropolymers, e.g.
teflon, in presence of oxygen yields
carbonyl fluoride (which hydrolyzes readily to HF and CO
2); other compounds may be formed as well, e.g.
carbon tetrafluoride,
hexafluoropropylene, and highly toxic
perfluoroisobutene
Perfluoroisobutene (PFIB) is the perfluorocarbon counterpart of the hydrocarbon isobutene and has the formula (CF3)2C=CF2. An alkene, it is a colorless gas that is notable as a highly toxic perfluoroalkene. Few simple alkenes are as toxic.
Safet ...
(PFIB).

Pyrolysis of burning material, especially
incomplete combustion
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combusti ...
or
smoldering
Smouldering (British English) or smoldering (American English; see spelling differences) is the slow, flameless form of combustion, sustained by the heat evolved when oxygen directly attacks the surface of a condensed-phase fuel. Many solid mate ...
without adequate oxygen supply, also results in production of a large amount of
hydrocarbons, both
aliphatic (
methane,
ethane,
ethylene
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds).
Ethylene i ...
,
acetylene
Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...
) and
aromatic (
benzene and its derivates,
polycyclic aromatic hydrocarbons; e.g.
benzo yrene">yrene, studied as a carcinogen, or
retene),
terpenes. It also results in the emission of a range of smaller oxygenated
volatile organic compounds (
methanol
Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...
,
acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
,
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
Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen atom. Chemical compounds containing such rings are also referred to as furans.
Furan is a colorless, flammable, highly ...
s and
furanone
2-Furanone is a heterocyclic organic compound. It is also known as γ-crotonolactone (GCL), as it is formally the lactone derived from γ-hydroxyisocrotonic acid. The chemical is colloquially called "butenolide", and is the parent structure for th ...
s.
Heterocyclic compound
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...
s may be also present. Heavier hydrocarbons may condense as
tar; smoke with significant tar content is yellow to brown. Combustion of solid fuels can result in the emission of many hundreds to thousands of lower volatility organic compounds in the aerosol phase. 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.
Presence of sulfur can lead to formation of gases like hydrogen sulfide,
carbonyl sulfide, sulfur dioxide,
carbon disulfide, and
thiols; 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:
aldehydes (e.g.
formaldehyde,
acrolein
Acrolein (systematic name: propenal) is the simplest unsaturated aldehyde. It is a colorless liquid with a piercing, acrid smell. The smell of burnt fat (as when cooking oil is heated to its smoke point) is caused by glycerol in the burning fa ...
, and
furfural
Furfural is an organic compound with the formula C4H3OCHO. It is a colorless liquid, although commercial samples are often brown. It has an aldehyde group attached to the 2-position of furan. It is a product of the dehydration of sugars, as occurs ...
), ketones,
alcohols
In chemistry, an alcohol is a type of organic compound that carries at least one hydroxyl () functional group bound to a saturated carbon atom. The term ''alcohol'' originally referred to the primary alcohol ethanol (ethyl alcohol), which is ...
(often aromatic, e.g.
phenol,
guaiacol,
syringol,
catechol, and
cresols),
carboxylic acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...
s (
formic acid
Formic acid (), systematically named methanoic acid, is the simplest carboxylic acid, and has the chemical formula HCOOH and structure . It is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. Es ...
,
acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
, etc.).
The visible
particulate matter
Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The ter ...
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
An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...
s. Particles of inorganic
salts may also be formed, e.g.
ammonium sulfate,
ammonium nitrate, or
sodium chloride
Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...
. Inorganic salts present on the surface of the soot particles may make them
hydrophilic. Many organic compounds, typically the
aromatic hydrocarbons, may be also
adsorb
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a fl ...
ed on the surface of the solid particles. Metal oxides can be present when metal-containing fuels are burned, e.g.
solid rocket
A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses solid propellants
Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine ...
fuels containing
aluminium.
Depleted uranium
Depleted uranium (DU; also referred to in the past as Q-metal, depletalloy or D-38) is uranium with a lower content of the fissile isotope than natural uranium.: "Depleted uranium possesses only 60% of the radioactivity of natural uranium, hav ...
projectiles after impacting the target ignite, producing particles of
uranium oxides.
Magnetic
Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particle ...
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. (Magnetic iron oxide nanoparticles can be also produced in the smoke from
meteorite
A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...
s burning in the atmosphere.) Magnetic
remanence
Remanence or remanent magnetization or residual magnetism is the magnetization left behind in a ferromagnetic material (such as iron) after an external magnetic field is removed. Colloquially, when a magnet is "magnetized", it has remanence. The ...
,
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.
Fly ash
Fly ash, flue ash, coal ash, or pulverised fuel ash (in the UK) plurale tantum: coal combustion residuals (CCRs)is a coal combustion product that is composed of the particulates (fine particles of burned fuel) that are driven out of coal-fired ...
is composed mainly of
silica and
calcium oxide.
Cenospheres are present in smoke from liquid hydrocarbon fuels. Minute metal particles produced by
abrasion can be present in engine smokes.
Amorphous silica particles are present in smokes from burning
silicone
A silicone or polysiloxane is a polymer made up of siloxane (−R2Si−O−SiR2−, where R = organic group). They are typically colorless oils or rubber-like substances. Silicones are used in sealants, adhesives, lubricants, medicine, cooking ...
s; small proportion of
silicon nitride particles can be formed in fires with insufficient oxygen. The silica particles have about 10 nm size, clumped to 70–100 nm aggregates and further agglomerated to chains.
Radioactive particles may be present due to traces of
uranium,
thorium, or other
radionuclide
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transfer ...
s in the fuel;
hot particles can be present in case of fires during
nuclear accident
A nuclear and radiation accident is defined by the International Atomic Energy Agency (IAEA) as "an event that has led to significant consequences to people, the environment or the facility. Examples include lethal effects to individuals, lar ...
s (e.g.
Chernobyl disaster
The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the No. 4 reactor in the Chernobyl Nuclear Power Plant, near the city of Pripyat in the north of the Ukrainian SSR in the Soviet Union. It is one of only two nuc ...
) or
nuclear war
Nuclear warfare, also known as atomic warfare, is a theoretical military conflict or prepared political strategy that deploys nuclear weaponry. Nuclear weapons are weapons of mass destruction; in contrast to conventional warfare, nuclear w ...
.
Smoke particulates, like other aerosols, are categorized into three modes based on particle size:
* nuclei mode, with
geometric mean
In mathematics, the geometric mean is a mean or average which indicates a central tendency of a set of numbers by using the product of their values (as opposed to the arithmetic mean which uses their sum). The geometric mean is defined as the ...
radius between 2.5 and 20 nm, likely forming by condensation of carbon
moieties.
*
accumulation mode
An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...
, ranging between 75 and 250 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
In the physics of aerosols, deposition is the process by which aerosol particles collect or deposit themselves on solid surfaces, decreasing the concentration of the particles in the air. It can be divided into two sub-processes: ''dry'' and ''w ...
, and the smoke damage in more distant areas outside of the room where the fire occurs is therefore primarily mediated by the smaller particles.
Aerosol of particles beyond visible size is an early indicator of materials in a preignition stage of a fire.
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
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pas ...
is present in emissions from
oil fired power plants and
refineries
A refinery is a production facility composed of a group of chemical engineering unit processes and unit operations refining certain materials or converting raw material into products of value.
Types of refineries
Different types of refineries ar ...
; oil plants also emit some
nickel. Coal combustion
produces emissions containing
aluminium,
arsenic,
chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal.
Chromium metal is valued for its high corrosion resistance and hardne ...
,
cobalt,
copper,
iron,
mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
,
selenium, and
uranium.
Traces of vanadium in high-temperature combustion products form droplets of molten
vanadates. These attack the
passivation layers on metals and cause
high temperature corrosion
High-temperature corrosion is a mechanism of corrosion that takes place when gas turbines, diesel engines, furnaces or other machinery come in contact with hot gas containing certain contaminants. Fuel sometimes contains vanadium compounds or su ...
, which is a concern especially for
internal combustion engines. 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
Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...
and are characteristic of
wood smoke; other markers are
syringol and derivates, and other
methoxy phenols.
Retene, a product of pyrolysis of
conifer
Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single ...
trees, is an indicator of
forest fire
A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire ...
s.
Levoglucosan is a pyrolysis product of
cellulose.
Hardwood
Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...
vs
softwood
file:Pinus sylvestris wood ray section 1 beentree.jpg, Scots Pine, a typical and well-known softwood
Softwood is wood from gymnosperm trees such as conifers. The term is opposed to hardwood, which is the wood from angiosperm trees. The main diff ...
smokes differ in the ratio of guaiacols/syringols. Markers for vehicle exhaust include
polycyclic aromatic hydrocarbons,
hopanes,
sterane
Sterane (cyclopentanoperhydrophenanthrenes) compounds are a class of tetracyclic compounds derived from steroids or sterols via diagenetic and catagenetic degradation and saturation. Steranes have an androstane skeleton with a side chain at carb ...
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.
Many compounds can be associated with particulates; whether by being
adsorbed on their surfaces, or by being dissolved in liquid droplets. Hydrogen chloride is well absorbed in the soot particles.
Inert particulate matter can be disturbed and entrained into the smoke. Of particular concern are particles of
asbestos
Asbestos () is a naturally occurring fibrous silicate mineral. There are six types, all of which are composed of long and thin fibrous crystals, each fibre being composed of many microscopic "fibrils" that can be released into the atmosphere b ...
.
Deposited
hot particles of
radioactive fallout and bioaccumulated radioisotopes can be reintroduced into the atmosphere by
wildfires and
forest fire
A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire ...
s; this is a concern in e.g. the
Zone of alienation containing contaminants from the
Chernobyl disaster
The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the No. 4 reactor in the Chernobyl Nuclear Power Plant, near the city of Pripyat in the north of the Ukrainian SSR in the Soviet Union. It is one of only two nuc ...
.
Polymers are a significant source of smoke. Aromatic
side groups, e.g. in
polystyrene
Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...
, 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 retardants decrease production of smoke. Higher degree of
cross-linking between the polymer chains has such effect too.
Visible and invisible particles of combustion

The
naked eye detects particle sizes greater than 7 µm (
micrometres).
Visible
Visibility, in meteorology, is a measure of the distance at which an object or light can be seen.
Visibility may also refer to:
* A measure of turbidity in water quality control
* Interferometric visibility, which quantifies interference contrast ...
particles emitted from a fire are referred to as smoke.
Invisible particles are generally referred to as gas or fumes. This is best illustrated when
toast
Toast most commonly refers to:
* Toast (food), bread browned with dry heat
* Toast (honor), a ritual in which a drink is taken
Toast may also refer to:
Places
* Toast, North Carolina, a census-designated place in the United States
Books
* '' ...
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
Smouldering (British English) or smoldering (American English; see spelling differences) is the slow, flameless form of combustion, sustained by the heat evolved when oxygen directly attacks the surface of a condensed-phase fuel. Many solid mate ...
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
A textile conservator is a conservator-restorer charged with the care, treatment, research, and preservation of textiles. Issues addressed by a textile conservator are generally related to the field of textile preservation, and include damage ca ...
companies specialize in restoring fabrics that have been damaged in a fire.
Dangers
Smoke from oxygen-deprived fires contains a significant concentration of compounds that are flammable. A cloud of smoke, in contact with atmospheric oxygen, therefore has the potential of being ignited – either by another open flame in the area, or by its own temperature. This leads to effects like
backdraft and
flashover.
Smoke inhalation is also a danger of smoke that can cause serious injury and death.
Many compounds of smoke from fires are highly toxic and/or irritating. The most dangerous is
carbon monoxide leading to
carbon monoxide poisoning, sometimes with the additive effects of
hydrogen cyanide
Hydrogen cyanide, sometimes called prussic acid, is a chemical compound with the formula HCN and structure . It is a colorless, extremely poisonous, and flammable liquid that boils slightly above room temperature, at . HCN is produced on an ...
and
phosgene
Phosgene is the organic chemical compound with the formula COCl2. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. Phosgene is a valued and important industrial building block, espe ...
. Smoke inhalation can therefore quickly lead to incapacitation and loss of consciousness. Sulfur oxides, hydrogen chloride and hydrogen fluoride in contact with moisture form
sulfuric
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
,
hydrochloric and
hydrofluoric acid
Hydrofluoric acid is a Solution (chemistry), solution of hydrogen fluoride (HF) in water. Solutions of HF are colourless, acidic and highly Corrosive substance, corrosive. It is used to make most fluorine-containing compounds; examples include th ...
, which are corrosive to both lungs and materials. When asleep the nose does not sense smoke nor does the brain, but the body will wake up if the lungs become enveloped in smoke and the brain will be stimulated and the person will be awoken. This does not work if the person is incapacitated or under the influence of drugs and/or alcohol.
Cigarette smoke
Tobacco smoke is a sooty aerosol produced by the incomplete combustion of tobacco during the smoking of cigarettes and other tobacco products. Temperatures in burning cigarettes range from about 400 °C between puffs to about 900 °C d ...
is a major modifiable risk factor for
lung disease,
heart disease
Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, hea ...
, 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 typically much less than that in cigarette smoke. One day of exposure to PM2.5 at a concentration of 880 μg/m3, such as occurs in Beijing, China, is the equivalent of smoking one or two cigarettes in terms of particulate inhalation by weight. The analysis is complicated, however, by the fact that the organic compounds present in various ambient particulates may have a higher carcinogenicity than the compounds in cigarette smoke particulates. Secondhand tobacco smoke is the combination of both sidestream and mainstream smoke emissions from a burning tobacco product. These emissions contain more than 50 carcinogenic chemicals. According to the United States
Surgeon General's 2006 report on the subject, "Short exposures to secondhand
obaccosmoke can cause blood platelets to become stickier, damage the lining of blood vessels, decrease coronary flow velocity reserves, and reduce heart variability, potentially increasing the risk of a heart attack". The American Cancer Society lists "heart disease, lung infections, increased asthma attacks, middle ear infections, and low birth weight" as ramifications of smoker's emission.

Smoke can obscure visibility, impeding occupant exiting from fire areas. In fact, the poor visibility due to the smoke that was in the
Worcester Cold Storage Warehouse fire in
Worcester, Massachusetts was the reason why the trapped rescue firefighters could not evacuate the building in time. Because of the striking similarity that each floor shared, the dense smoke caused the firefighters to become disoriented.
Corrosion
Smoke can contain a wide variety of chemicals, many of them aggressive in nature. Examples are
hydrochloric acid and
hydrobromic acid, produced from
halogen
The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this group is ...
-containing
plastics and
fire retardant
A fire retardant is a substance that is used to slow down or stop the spread of fire or reduce its intensity. This is commonly accomplished by chemical reactions that reduce the flammability of fuels or delay their combustion. Fire retardants m ...
s,
hydrofluoric acid
Hydrofluoric acid is a Solution (chemistry), solution of hydrogen fluoride (HF) in water. Solutions of HF are colourless, acidic and highly Corrosive substance, corrosive. It is used to make most fluorine-containing compounds; examples include th ...
released by
pyrolysis of
fluorocarbon
Fluorocarbons are chemical compounds with carbon-fluorine bonds. Compounds that contain many C-F bonds often has distinctive properties, e.g., enhanced stability, volatility, and hydrophobicity. Fluorocarbons and their derivatives are commerci ...
fire suppression agent
A fire retardant is a substance that is used to slow down or stop the spread of fire or reduce its intensity. This is commonly accomplished by chemical reactions that reduce the flammability of fuels or delay their combustion. Fire retardants m ...
s,
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
from burning of
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
-containing materials,
nitric acid from high-temperature fires where
nitrous oxide gets formed,
phosphoric acid and
antimony compounds from P and Sb based fire retardants, and many others. Such
corrosion is not significant for structural materials, but delicate structures, especially
microelectronics, are strongly affected. Corrosion of
circuit board traces, penetration of aggressive chemicals through the casings of parts, and other effects can cause an immediate or gradual deterioration of parameters or even premature (and often delayed, as the corrosion can progress over long time) failure of equipment subjected to smoke. Many smoke components are also
electrically conductive
Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...
; deposition of a conductive layer on the circuits can cause
crosstalk
In electronics, crosstalk is any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, induc ...
s and other deteriorations of the operating parameters or even cause short circuits and total failures.
Electrical contacts can be affected by corrosion of surfaces, and by deposition of
soot and other conductive particles or nonconductive layers on or across the contacts. Deposited particles may adversely affect the performance of
optoelectronics by absorbing or scattering the light beams.
Corrosivity of smoke produced by materials is characterized by the corrosion index (CI), defined as material loss rate (angstrom/minute) per amount of material gasified products (grams) per volume of air (m
3). It is measured by exposing strips of metal to flow of combustion products in a test tunnel. Polymers containing halogen and
hydrogen (
polyvinyl chloride,
polyolefin
A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More speciali ...
s with halogenated additives, etc.) have the highest CI as the corrosive acids are formed directly with water produced by the combustion, polymers containing halogen only (e.g.
polytetrafluoroethylene
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chemour ...
) have lower CI as the formation of acid is limited to reactions with airborne humidity, and halogen-free materials (polyolefins,
wood) have the lowest CI.
However, some halogen-free materials can also release significant amount of corrosive products.
Smoke damage to electronic equipment can be significantly more extensive than the fire itself.
Cable fires are of special concern;
low smoke zero halogen
Low smoke zero halogen or low smoke free of halogen (LSZH or LSOH or LS0H or LSFH or OHLS or ZHFR) is a material classification typically used for cable jacketing in the wire and cable industry. LSZH cable jacketing is composed of thermoplastic or ...
materials are preferable for cable insulation.
When smoke comes into contact with the surface of any substance or structure, the chemicals contained in it are transferred to it. The corrosive properties of the chemicals cause the substance or structure to decompose at a rapid rate. Certain materials or structures absorb these chemicals, which is why clothing, unsealed surfaces, potable water, piping, wood, etc., are replaced in most cases of structural fires.
Health effects of wood smoke
Wood smoke is a major source of
air pollution,
especially
particulate pollution
Particulate pollution is pollution of an environment that consists of particles suspended in some medium. There are three primary forms: atmospheric particulate matter, marine debris, and space debris. Some particles are released directly from a sp ...
,
[pollution by polycyclic aromatic hydrocarbons (PAHs)] and volatile organic compounds (VOCs)[ such as formaldehyde.]
In the United Kingdom domestic combustion, especially for industrial uses, is the largest single source of PM2.5 annually. In some towns and cities in New South Wales, wood smoke may be responsible for 60% of fine particle air pollution in the winter. A year-long sampling campaign in Athens, Greece found a third (31%) of PAH urban air pollution to be caused by wood-burning, roughly as much as that of diesel
Diesel may refer to:
* Diesel engine, an internal combustion engine where ignition is caused by compression
* Diesel fuel, a liquid fuel used in diesel engines
* Diesel locomotive, a railway locomotive in which the prime mover is a diesel engin ...
and oil (33%) and gasoline (29%). It also found that wood-burning is responsible for nearly half (43%) of annual PAH lung cancer-risk compared to the other sources and that wintertime PAH levels were 7 times higher than in other seasons, presumably due to an increased use of fireplaces and heaters. The largest exposure events are periods during the winter with reduced atmospheric dispersion to dilute the accumulated pollution , in particular due to the low wind speeds.
Wood smoke (for example from wildfires) can cause lung damage, artery damage and DNA damage leading to cancer, other respiratory and lung disease and cardiovascular disease. Air pollution, particulate matter and wood smoke may also indirectly cause brain damage because of particulates breaching the cardiovascular system and into the brain, which can increase the risk of developmental disorders, neurodegenerative disorders mental disorders, and suicidal behavior,[ although studies on the link between depression and some air pollutants are not consistent. At least one study has identified "the abundant presence in the human brain of magnetite nanoparticles that match precisely the high-temperature magnetite nanospheres, formed by combustion and/or friction-derived heating, which are prolific in urban, airborne particulate matter (PM)." Air pollution has also been linked to a range of other psychosocial problems.][
]
Measurement
As early as the 15th century Leonardo da Vinci commented at length on the difficulty of assessing smoke, and distinguished between black smoke (carbonized particles) and white 'smoke' which is not a smoke at all but merely a suspension of harmless water particulates.
Smoke from heating appliances is commonly measured in one of the following ways:
In-line capture. A smoke sample is simply sucked through a filter which is weighed before and after the test and the mass of smoke found. This is the simplest and probably the most accurate method, but can only be used where the smoke concentration is slight, as the filter can quickly become blocked.
The ASTM smoke pump is a simple and widely used method of in-line capture where a measured volume of smoke is pulled through a filter paper and the dark spot so formed is compared with a standard.
Filter/dilution tunnel. A smoke sample is drawn through a tube where it is diluted with air, the resulting smoke/air mixture is then pulled through a filter and weighed. This is the internationally recognized method of measuring smoke from combustion.
Electrostatic precipitation. The smoke is passed through an array of metal tubes which contain suspended wires. A (huge) electrical potential is applied across the tubes and wires so that the smoke particles become charged and are attracted to the sides of the tubes. This method can over-read by capturing harmless condensates, or under-read due to the insulating effect of the smoke. However, it is the necessary method for assessing volumes of smoke too great to be forced through a filter, i.e., from bituminous coal
Bituminous coal, or black coal, is a type of coal containing a tar-like substance called bitumen or asphalt. Its coloration can be black or sometimes dark brown; often there are well-defined bands of bright and dull material within the seams. It ...
.
Ringelmann scale
The Ringelmann scale is a scale for measuring the apparent density or opacity of smoke.
It was developed by a French professor of agricultural engineering Maximilien Ringelmann of La Station d'Essais de Machines in Paris, who first specified th ...
. A measure of smoke color. Invented by Professor Maximilian Ringelmann
Maximilian, Maximillian or Maximiliaan (Maximilien in French) is a male given name.
The name " Max" is considered a shortening of "Maximilian" as well as of several other names.
List of people
Monarchs
*Maximilian I, Holy Roman Emperor (1459� ...
in Paris in 1888, it is essentially a card with squares of black, white and shades of gray which is held up and the comparative grayness of the smoke judged. Highly dependent on light conditions and the skill of the observer it allocates a grayness number from 0 (white) to 5 (black) which has only a passing relationship to the actual quantity of smoke. Nonetheless, the simplicity of the Ringelmann scale means that it has been adopted as a standard in many countries.
Optical scattering. A light beam is passed through the smoke. A light detector is situated at an angle to the light source, typically at 90°, so that it receives only light reflected from passing particles. A measurement is made of the light received which will be higher as the concentration of smoke particles becomes higher.
Optical obscuration. A light beam is passed through the smoke and a detector opposite measures the light. The more smoke particles are present between the two, the less light will be measured.
Combined optical methods. There are various proprietary optical smoke measurement devices such as the ' nephelometer' or the ' aethalometer' which use several different optical methods, including more than one wavelength of light, inside a single instrument and apply an algorithm to give a good estimate of smoke. It has been claimed that these devices can differentiate types of smoke and so their probable source can be inferred, though this is disputed.
Inference from carbon monoxide. Smoke is incompletely burned fuel
A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...
, carbon monoxide is incompletely burned carbon, therefore it has long been assumed that measurement of CO in flue gas (a cheap, simple and very accurate procedure) will provide a good indication of the levels of smoke. Indeed, several jurisdictions use CO measurement as the basis of smoke control. However it is far from clear how accurate the correspondence is.
Medicinal smoking
Throughout recorded history, humans have used the smoke of medicinal plants to cure illness. A sculpture from Persepolis shows Darius the Great
Darius I ( peo, 𐎭𐎠𐎼𐎹𐎺𐎢𐏁 ; grc-gre, Δαρεῖος ; – 486 BCE), commonly known as Darius the Great, was a Persian ruler who served as the third King of Kings of the Achaemenid Empire, reigning from 522 BCE until his d ...
(522–486 BC), the king of Persia, with two censers in front of him for burning Peganum harmala and/or sandalwood Santalum album, which was believed to protect the king from evil and disease. More than 300 plant species in 5 continents are used in smoke form for different diseases. As a method of drug administration
A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field and rel ...
, smoking is important as it is a simple, inexpensive, but very effective method of extracting particles containing active agents. More importantly, generating smoke reduces the particle size to a microscopic scale thereby increasing the absorption of its active chemical principles.
References
Sources
*
External links
Burning Issues wood smoke Site
Shedding new light on wood smoke
https://www.infographicview.com/things-you-need-to-know-about-smoke.html/ 7 things you need to know about smoke detectors]
{{Authority control
Smoke,
Fire