A smoke composition is a pyrotechnic composition designed primarily to generate

smoke 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 entrainment (engineering), entrained or otherwise mixed into the mass. It is commo ...

. Smoke compositions are used as obscurants or for generation of signaling smokes. Some are used as a payload of

smoke bomb A smoke bomb is a firework designed to produce a large amount of smoke upon ignition. History Early Japanese history saw the use of a rudimentary form of the smoke bomb. Explosives were common in Japan during the Mongol invasions of the 13 ...

s and

smoke grenade Smoke grenades used at demonstrations in Paris, 2008 upBritish L83A1 Smoke Grenade manufactured in May 2008. This grenade has already been used. A smoke grenade is a canister-type grenade used as a signaling device, target or landing zone mark ...

Obscurants

Smoke compositions used as obscurants generate large amount of thick, usually white, smoke. The most common smoke composition for pyrotechnic generation of

smoke screen A smoke screen is smoke released to mask the movement or location of military units such as infantry, tanks, aircraft, or ships. Smoke screens are commonly deployed either by a canister (such as a grenade) or generated by a vehicle (such as a ...

s is the zinc chloride smoke mixture (HC).

Zinc chloride smoke

Zinc chloride smoke is grey-white and consists of tiny particles of

zinc chloride Zinc chloride is the name of inorganic chemical compounds with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. This salt is hygroscopic and e ...

. The most common mixture for generating these is the zinc chloride smoke mixture (HC), consisting of

hexachloroethane Hexachloroethane, also known as perchloroethane is the organochlorine compound with the chemical formula . It is white solid at room temperature with a camphor-like odor. It has been used by the military in smoke compositions, such as base-eject ...

, grained

aluminium Aluminium (aluminum in AmE, American and CanE, Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately o ...

and

zinc oxide Zinc oxide is an inorganic compound with the Chemical formula, formula . It is a white powder that is insoluble in water. ZnO is used as an additive in numerous materials and products including cosmetics, food supplements, rubbers, plastics, ceram ...

. The smoke consists of zinc chloride, zinc oxychlorides, and

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the dig ...

, which absorb the

moisture Moisture is the presence of a liquid, especially water, often in trace amounts. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some commercial products. Moisture also refers to the amount of water vapo ...

in the air. The smoke also contains traces of organic chlorinated compounds,

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, es ...

carbon monoxide Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

, and

chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is ...

. Its toxicity is caused mainly by the content of strongly acidic hydrochloric acid, but also due to thermal effects of reaction of zinc chloride with water. These effects cause

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classif ...

s of the

mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It i ...

s of the upper airways. Damage of the lower airways can manifest itself later as well, due to fine particles of zinc chloride and traces of phosgene. In high concentrations the smoke can be very dangerous when inhaled. Symptoms include

dyspnea Shortness of breath (SOB), also medically known as dyspnea (in AmE) or dyspnoea (in BrE), is an uncomfortable feeling of not being able to breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing disc ...

, retrosternal pain, hoarseness, stridor, lachrymation,

cough A cough is a sudden expulsion of air through the large breathing passages that can help clear them of fluids, irritants, foreign particles and microbes. As a protective reflex, coughing can be repetitive with the cough reflex following three ph ...

, expectoration, and in some cases haemoptysis. Delayed

pulmonary edema Pulmonary edema, also known as pulmonary congestion, is excessive liquid accumulation in the tissue and air spaces (usually alveoli) of the lungs. It leads to impaired gas exchange and may cause hypoxemia and respiratory failure. It is du ...

cyanosis Cyanosis is the change of body tissue color to a bluish-purple hue as a result of having decreased amounts of oxygen bound to the hemoglobin in the red blood cells of the capillary bed. Body tissues that show cyanosis are usually in locations ...

bronchopneumonia Bronchopneumonia is a subtype of pneumonia. It is the acute inflammation of the bronchi, accompanied by inflamed patches in the nearby lobules of the lungs. citing: Webster's New World College Dictionary, Fifth Edition, Copyright 2014 It is ofte ...

may develop. The smoke and the spent canisters contain suspected

carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subst ...

s. The prognosis for the casualties depends on the degree of the pulmonary damage. All exposed individuals should be kept under observation for 8 hours. Most affected individuals recover within several days, with some symptoms persisting for up to 1-2 weeks. Severe cases can suffer of reduced pulmonary function for some months, the worst cases developing marked dyspnea and cyanosis leading to death. Respirators are required for people coming into contact with the zinc chloride smoke.

White phosphorus

White phosphorus Elemental phosphorus can exist in several allotropes, the most common of which are white and red solids. Solid violet and black allotropes are also known. Gaseous phosphorus exists as diphosphorus and atomic phosphorus. White phosphorus Whi ...

is a popular base for smoke production. It is used in artillery shells, bombs, and grenades.

Signalling

A colored smoke composition can be used for signalling. These are usually based on a low-temperature burning pyrotechnic composition, mixed with a dye that gets vaporized and creates large, colored smoke particles. The composition is often based on an oxidizer (e.g. potassium chlorate,

potassium nitrate Potassium nitrate is a chemical compound with the chemical formula . This alkali metal nitrate salt is also known as Indian saltpetre (large deposits of which were historically mined in India). It is an ionic salt of potassium ions K+ and ni ...

, or

potassium perchlorate Potassium perchlorate is the inorganic salt with the chemical formula K Cl O4. Like other perchlorates, this salt is a strong oxidizer although it usually reacts very slowly with organic substances. This, usually obtained as a colorless, crys ...

), a fuel (e.g.

lactose Lactose is a disaccharide sugar synthesized by galactose and glucose subunits and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from ' (gen. '), the Latin word for milk, plus the suffix ...

), an optional coolant (e.g. sodium bicarbonate), and one or more dyes.

Fire extinguishing

Smoke with a suitable composition can be used as a fire suppression agent. A pyrotechnic composition similar to

black powder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate ( saltpeter) ...

, composed of 15% charcoal and 85%

, generates thick smoke composed of particles of mainly

potassium carbonate Potassium carbonate is the inorganic compound with the formula K2 CO3. It is a white salt, which is soluble in water. It is deliquescent, often appearing as a damp or wet solid. Potassium carbonate is mainly used in the production of soap and gl ...

, which has fire extinguishing properties. Two-kilograms

s, thrown into burning rooms through plate-glass windows, have been used by some European firefighters.{{Cite book , url=https://books.google.com/?id=yxRyOf8jFeQC&pg=PA85&dq=popcorning&cd=22#v=onepage&q=popcorning&f=false , title = The Chemistry of Fireworks, isbn = 9780854041275, last1 = Russell, first1 = Michael S., year = 2009

Dispersion of chemicals

Smoke compositions can be used also for creating

aerosol An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog or mist, dust, forest exudates, and geyser steam. Examples of ant ...

of other materials than dyes. Generally the same type of pyrotechnic composition as for colored smokes is used, with the dye being replaced by the desired chemical. The devices usually have the form of

s. The best known such application of smoke compositions is in

riot control Riot control measures are used by law enforcement, military, paramilitary or security forces to control, disperse, and arrest people who are involved in a riot, unlawful demonstration or unlawful protest. If a riot is spontaneous and irra ...

, for dispersion of lachrymatory agents. The agent used is most often

CS gas The compound 2-chlorobenzalmalononitrile (also called ''o''-chlorobenzylidene malononitrile; chemical formula: C10H5ClN2), a cyanocarbon, is the defining component of tear gas commonly referred to as CS gas, which is used as a riot control agen ...

, with less used alternatives CR gas, CN gas and Adamsite. In agriculture, smoke compositions are used to disperse insecticides and fungicides. Some agents used in this manner are

permethrin Permethrin is a medication and an insecticide. As a medication, it is used to treat scabies and lice. It is applied to the skin as a cream or lotion. As an insecticide, it can be sprayed onto clothing or mosquito nets to kill the insects tha ...

cypermethrin Cypermethrin (CP) is a synthetic pyrethroid used as an insecticide in large-scale commercial agricultural applications as well as in consumer products for domestic purposes. It behaves as a fast-acting neurotoxin in insects. It is easily degrad ...

chlorpyrifos Chlorpyrifos (CPS), also known as Chlorpyrifos ethyl, is an organophosphate pesticide that has been used on crops, animals, and buildings, and in other settings, to kill several pests, including insects and worms. It acts on the nervous systems ...

, imazalil, et

and some

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 ...

agents. Smoke compositions can be also used for weather modification, namely

cloud seeding Cloud seeding is a type of weather modification that aims to change the amount or type of precipitation that falls from clouds by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical ...

, to provide

cloud condensation nuclei Cloud condensation nuclei (CCNs), also known as cloud seeds, are small particles typically 0.2 µm, or one hundredth the size of a cloud droplet. CCNs are a unique subset of aerosols in the atmosphere on which water vapour condenses. This c ...

for the moisture to precipitate.

References

Pyrotechnic compositions Smoke Fire suppression agents