Weapons Law Encyclopedia

Riot control agents

Chemical irritant compounds have been used widely throughout history. They were allegedly used against the Ambracians by Marcus Fulvius in the 2nd Century BC and by the Byzantines to harass their enemies. Further, Plutarch, a Roman historian, describes the use of ‘an irritant cloud’ by a Roman general to drive an enemy from a cave in Spain.J. P. Robinson, The Problem of Chemical & Biological Warfare, Vol. 1 in The Rise of CB Weapons, Humanities Press, 1971 in F. R. Sidell, ‘Chapter 12: Riot Control Agents’, in The Textbook of Military Medicine: Medical Aspects of Chemical & Biological Warfare, 1997.

The development of the chemicals used in today’s RCAs (CN, CR, CS, OC, and PAVA) began in the late 1800s with the synthesis of CN by German chemist Carl Graebe.H. Salem et al., ‘Chapter 13: Riot Control Agents’, in M. Lenhart (ed.), Textbooks of Military Medicine: Medical Aspects of Chemical Warfare, US, 2008. According to Salem et al. (2008), CN was the RCA of choice from the latter part of the 1914–18 War until the 1950s when it was replaced with CS.  Despite this replacement, CN is still in use today and is sold by a number of companies worldwide in the form of self-defence sprays and tear gas grenades/canisters. A total of 67 states parties to the CWC declared holdings of CN in 2011.Report of the OPCW on the Implementation of the Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction in 2011. CN has been recently used in:

Yemen (2011) – images show fired US-made CN canisters photographed after protests in the capital Sana’a.L. Loveluck, Yemen & the War on Terror, Varsity Blogs, 13 March 2011. and in the Red Sea city of Hodeidah. Yemen Rights Monitor, Protests March 16, Hodeidah, 16 March 2011.
Mexico (2007) – images show fired US-made CN canisters photographed in Oaxaca in 2007. El Enemigo Comun (2007) Corporate Criminals in Oaxaca, reprinted through IndyMedia, 21 July 2007.
Panama (2001) – images show fired US-made CN canisters photographed in the capital Panama City. E. Jackson, ‘Turmoil in the Capital’, Panama News, May 2001.

CS was first synthesised by British scientists Corson and Stoughton in the 1920s but was not widely accepted for use as an RCA until after 1945 when it was discovered that it was ‘less toxic but more potent than CN’.Salem et al. (2008) (op. cit.). Today, CS is the most widely used RCA, and 111 states parties to the CWC have declared holding CS.Report of the OPCW on the Implementation of the Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction in 2011. CS has been recently used in many countries, such as:

Azerbaijan (2013) – Israeli-made CS smoke canisters photographed after a demonstration in Baku in March 2013 A. Kazimova (2013) 10 mart aksiyaindaki qulaqbatiran LRAD, Azadliq Radiosu, 13 March 2013.
Bahrain (2012) – images show Brazilian & South African CS gas canisters photographed in Bahrain.
Equatorial Guinea (2012) – French-made CS gas canister photographed being fired by police at Bata Stadium, Bata, January 2012 A. Dalsh (2012) Reuters image ID: GM1E81M1M9701).
Kenya (2012) – French-made CS gas canisters photographed on the belt of a police officer standing guard outside a damaged shop during unrest in Mombasa, August 2012AP Image reprinted by Yahoo News (2012) Riot Police Stand Guard Outside a Damaged Shop in Mombasa, 27 August 2012.
Malaysia (2012) – US-made CS canister photographed after the Bersih 3.0 sit-in rally in Kuala Lumpar, Malaysia, April 2012 PDRM Blog (2012) PDRM 2.0, 30 April 2012.
Peru (2012) – CS gas canisters photographed on the vest of a Peruvian police officer during a protest against a mining project in Cajamarca, Peru on 6 August 2012. The canisters appear visually similar to those made in Spain, and under licence from the Spanish companies in Venezuela E. Benavides (2012) Getty Image ID: 147956867.
Senegal (2012) – French-made CS gas canisters photographed on the vest of a Senegalese police officer during demonstrations in Dakar, 19 February 2012 Seyllou (2012) Getty Image ID: 139311166.
Sudan (2012) – Chinese-made CS gas canister photographed in Sudan during protests in June 2012 Images collated from various sources by Right Now I/O.
Turkey (2013) – images show fired US-, Brazilian-, and South Korean-manufactured CS canisters/grenades after protests in Istanbul, in 2013 Brown Moses (2013) Imgur Collection.

CR, the most recently synthesised but least widely used chemical in use in RCAs today, was developed in the UK in 1962 by Higginbottom and Suchitzsky. It is six times more powerful than CS and 30 times more powerful than CN.Omega Foundation, Crowd Control Technologies: An Appraisal of Technologies for Political Control, 2000. While not widely used today, there have been unconfirmed allegations of use of CR in Egypt (2011) and in Bahrain (2012);P. Beaumont and J. Domokos, ‘Egyptian Military using “More Dangerous” Tear Gas on Tahrir Square Protesters’, The Guardian, 23 November 2011; G. Carlstrom, ‘Bahraini Villagers Fear Effects of Tear Gas’, Aljazeera, 2 April 2012. and it is still currently manufactured in the Czech Republic by the Oritest Group and recently manufactured in India by Tear Smoke Unit, although their CR and CN products had (at time of writing) been removed from their respective websites. Less recently, reports indicate that South Africa manufactured more than 20 tons of CR for use by soldiers policing black townships in the 1980s as, according to Amnesty International, ‘the government realised it was easy for people to deal with the effects of CS gas.’Amnesty International, The Pain Merchants: Security Equipment and its use in Torture and Ill-Treatment, ACT 40/008/2003, 2003. A report from 2005 indicates that CR was secretly authorised by the British government for use in prisons in Northern Ireland in the 1970s in the event of attempted mass breakout, and allegedly used in 1974 to quell rioting at Long Kesh prison, nine miles southwest of Belfast.C. Morrison and M. Bright, ‘Secret Gas was Issued for IRA Prison Riots’, The Observer, 23 January 2005, cited in Salem et al (2008 (op. cit.).

OC was developed in 1960 at the University of Georgia by Jenkins and Hayes. It is derived from the naturally occurring capsicum species of plant and as such, the components of it can vary depending on the crop chosen to manufacture the product.Omega Foundation (2000), op. cit.). OC was originally developed as an animal repellent and sold under the brand name HALT! In the late 1980s, the firearms training unit at the FBI Academy in Virginia, US, undertook a three-year study on OC and subsequently authorized its use by its special agents and SWAT teams to ‘control unruly subjects without having to resort to a physical confrontation or deadly force’.Safety Gear HQ, ‘The History of Pepper Spray’, undated but accessed in October 2013.

PAVA is a capsaicinoid that occurs naturally as a minor component in certain varieties of pepper; it can be synthetically produced. PAVA used in RCAs is predominantly sourced as a synthetic formulation and as such has a consistent strength and composition.Haber et al., Human Effectiveness & Risk Characterisation of OC & PAVA Handheld Devices, Air Force Research Laboratory, May 2007. PAVA is ‘believed to have similar but safer effects … than the natural form of OC’.Salem et al (2008) (op. cit.)

OC and PAVA have become widely used by law enforcement officials for both self-protection and crowd management. Recent examples of their use include:

Bahrain (2012) – images show a Bahraini police officer spraying a woman in the face with a handheld pepper spray during anti-government protests in Manama, 12 October  2012.L. Davidson, ‘Violence Rapidly Escalating in Bahrain’, Washington Post, 12 October 2012.
Brazil (2013) – images show a Brazilian police officer spraying a protester with what appear to be a Brazilian-made handheld pepper spray in Rio de Janeiro.V. Caviano (2013) reprinted on the BBC website, Day in Pictures 18 June 2013.
Israel (2012) – images show Israeli border police officers using handheld pepper sprays whilst detaining a protester in Jerusalem, March/April 2012 A. Awad (2012) reprinted on the BBC website, Week in Pictures: 31 March – 6 April 2012.
Turkey (2013) – images show police using backpack-style sprayers to disperse crowds during protests, and using pepper spray in their water cannons, in Istanbul in May and June 2013 L. Harding (2013) Turkey’s Resistance Image Forged as Pepper Spray Burns Woman in Red Dress, The Guardian, 5 June 2013, and Facebook (2013) Photos of Police Adding JENIX Pepper Spray to the Water from the TOMAs Water Cannons, 15 June 2013.
US (2011) – images and video show University of California campus police officers dousing peaceful sit-in protesters with pepper spray, November 2011 BBC News (2011) Pepper Spray: US Campus Police Suspended, BBC News Online, 20 November 2011.

Last updated on: 20 July 2017

Of the most commonly used RCAs today, CN, CS, CR, and PAVA, are crystalline solids at room temperature, and OC is an oil. They are delivered in relatively low concentrations, in several ways:

As a smoke or powder – many hand-thrown or weapon fired products are available which deliver either a dense cloud of irritant smoke or a direct localised burst of irritant powder. These include:

Grenades which are activated by a fuse and can be hand-thrown or weapon fired via grenade launchers or ‘launching cups’ which fit over the muzzle of conventional shotguns or rifles allowing them to fire larger calibre ammunition. Irritant is dispersed via hot gases and smoke produced through pyrotechnic burning of the payload. Manufactured worldwide in states such as Argentina, Brazil, China, India, the Republic of Korea, and the USA, grenades most commonly contain CS but are also available containing CN, CR and OC. These are designed to be fired at the ground where they release their irritant into the surrounding area.

Cartridges consist of a cartridge case containing either a projectile which is expelled, or the irritant load; like ammunition for conventional arms, they must be fired from a weapon. They range from 12 gauge shotgun rounds up to 40mm cartridges and can be fired from a range of devices including shotguns and a wide variety of specially designed launchers (often called ‘riot guns’). The projectiles have a range of up to 100 metres and once fired a pyrotechnic charge initiates burning to expel the irritant, or a blast charge initiates to disperse powdered irritant. ‘Muzzle blast’ cartridges expel powdered irritant directly from the muzzle of the weapon and are designed for close in fire up to approximately 10 metres. Some cartridges are designed to be fired at the ground where they release their irritant into the surrounding area; however, ‘direct impact projectiles’ are also available which are designed to be fired directly at an individual, which on impact release a small localised burst of powdered irritant combining kinetic impact with irritant effect. Cartridges most commonly contain CS but are also available containing CN, CR, and OC.

‘Pepperball’ and other specially designed projectiles, typically containing OC or PAVA, are designed to be fired directly at an individual using a high pressure air gun. Some projectiles, such as the US-made ‘Pepperball’ projectiles are similar in design to paintball projectiles used for recreational purposes (i.e. a small gel ball containing powdered irritant which splits open on impact releasing a small cloud of irritant). The FN303, manufactured in Belgium by FN Herstal and under licence in the US by FNH USA, consists of a fin-stabilized polystyrene projectile with a bismuth forward payload which, like their paintball-style counterparts, split open on impact to release the irritant payload.

‘Wide-area’ RCA delivery mechanisms including multiple munition launchers, mortar munitions, artillery projectiles, heliborne munition dispensers, cluster munitions, unmanned aerial or ground vehicles, among others, are designed to disperse large amounts of RCAs over wide areas and/or extended distances. These products predominantly contain CS, although others containing CN, CR, and OC have also been developed. The development of certain forms of wide-area RCA delivery mechanisms is a cause for concern given the dangers of: (a) employment of inherently inappropriate munitions for law enforcement; (b) proliferation to and misuse by non-state actors; (c) misuse to facilitate human rights violations; (d) potential employment in armed conflict; and (e) their potential use in chemical weapons programmes. Certain forms of ‘wide-area’ RCA delivery mechanisms may have utility in large scale law enforcement situations provided they meet the CWC ‘types and quantities’ provision and are employed in conformity with human rights standards. Other forms of ‘wide-area’ RCA means of delivery appear to be completely inappropriate for law enforcement. Such means of delivery could inherently breach the CWC ‘types and quantities’ provision and/or the prohibition on the use of RCAs as a ‘method of warfare’.For further discussion see: M. Crowley, Drawing the Line: Regulation of ‘Wide Area’ Riot Control Agents under the Chemical Weapons Convention, Report, 2013. Products of concern have been manufactured in a range of countries since the coming into force of the CWC in 1997, including China, India, the Russian Federation, Serbia, Turkey, and the USA.

As a liquid spray or foam, having been dissolved in a suitable solvent, the irritant is then sprayed or expelled from a range of devices. These include:

Handheld Sprays (aerosols) which usually contain OC or PAVA but are also available in CS, CN, CR, or a mixture thereof. Typically ranging in capacity from 25 millilitres up to one litre. They are manufactured worldwide and are widely used for law enforcement purposes, but also by civilians as personal protection sprays.

Larger ‘over the shoulder’ or ‘backpack-style’ sprayers disperse larger amounts of irritant with a capacity of up to several litres. They commonly contain OC or CS, or an OC-CS mixture. These larger sprayers have been used for law enforcement purposes in States such as Australia, DR Congo, Greece, Mexico, Peru, Turkey, Uganda, and the USA, and are manufactured in China, Germany, Israel, Poland, and the US, among others.

Confined-area extraction devices are predominantly manufactured in the USA and consist of a handheld spray with a ‘wand’ attachment for dispersal of OC spray into a confined area such as a cell, closet, or vehicle, etc.

Water cannon – most models of water cannon are manufactured with two or three separate tanks; the largest for the water and then one or two smaller additional tanks which can contain RCAs (predominantly CS or OC) and/or dye marking products which are mixed with the water for dispersal. As most of the RCAs are unstable and insoluble in water, the irritant is injected into the water stream at the last moment. Water cannon with tanks for RCA dispersal are manufactured in states such as China, Israel, the Republic of Korea, the Russian Federation, and the USA, among others.

As a vapour fog or irritant cloud, having been mixed with a solvent to produce a dense fog or cloud, they are usually dispersed via:

Fixed delivery systems – which are usually installed in secure rooms or places of detention, they disperse CS or OC into an enclosed space via remote control. They are manufactured in Germany and the USA, among others.

Aerosol grenades are a newer type of delivery mechanism for OC, CS or an OC/CS mix. They are a small aerosol with a single activation that empties the entire contents in one burst. They have been advertised as being suitable for use in confined spaces in order to force an individual or group to leave the space, as an area denial system (i.e. to deny access to an enclosed space), and for crowd control purposes. They are predominantly manufactured in the USA.

Hand-held ‘foggers’ – which have been promoted for use during crowd control or law enforcement situations. Mostly manufactured in the USA, hand-held ‘foggers’ can disperse OC, CS, or CN.

Last updated on: 20 July 2017

RCAs are intended to cause temporary incapacitation through sensory irritation; the effects of which disappear within a short time following termination of exposure.

CS, CN, and CR all have similar effects causing a ‘burning sensation in the eyes … severe irritation of the respiratory tract, burning pain in the nose, sneezing, soreness and tightness of chest. Even very light exposure can cause a rapid rise in blood pressure, and as this increases, gagging, nausea and vomiting occur’.H. Hu et al. (1989) 'Tear Gas: Harassing Agent or Toxic Chemical?', Journal of the American Medical Association, 1989, 262:660-3, in Amnesty International (2003) (op. cit.).

OC and PAVA (like CS, CN and CR) ‘interact with sensory nerve receptors in skin or mucosae to produce local sensation (discomfort, itching, burning sensation, or pain) … The principle effects of these agents are on the eye, respiratory tract, and skin ... on the eyes, depending on the concentration, the effects are local itching, discomfort, or pain with excessive lacrimation [tearing] and blepharospasm [involuntary tight closure of the eyes]’.H. Salem et al. (2008) (op. cit.).

Conditions affecting an individual’s reaction to the effects of RCAs include, ‘excessive application of the agent, delivery in an enclosed space, prolonged exposure (as when the victim cannot flee), a high minute ventilation (as during a fight), and (for skin reactions) high temperature and relative humidity’.A. R. Hill et al. (2000) Medical Hazards of the Tear Gas CS: A Case of Persistent, Multisystem, Hypersensitivity Reaction and Review of the Literature, Medicine 79:234-40, 2000.

Unintended effects of the use of these types of RCAs include contact dermatitis, skin blistering, pressure injury to the eyes, bronchoconstriction, and death.Haber et al (2007) (op. cit.), Levin, R et al (1973) Contact Sensitization to CS, A Riot Control Agent, Edgewood Arsenal, Aberdeen Proving Ground, Maryland, November 1973, and Salem, H et al (2008) (op. cit.).

The solvents used to dissolve the chemical irritants can also be harmful. Studies of OC sprays found that some contained toxic solvents: one individual who was exposed to a training spray that contained the substance trichloroethylene, but no OC, went on to develop corneal erosions, with alteration of vision that lasted two days, while use of a Russian-manufactured pepper spray containing unidentified solvents caused ‘severe chemical burns’ and eye damage lasting more than six weeks.M. Holopainen et al. (2003) Toxic Carriers in Pepper Sprays may Cause Corneal Erosion, Toxicology and Applied Pharmacology 186 (2003) 155–162). Concerns have also been expressed about the carcinogenic potential of the solvent MIBK, used to deliver CS (Rappert, B (2003) Health and Safety in Policing: Lessons from the Regulation of CS Sprays in the UK, Social Science & Medicine, 56 (2003) 1273.

Further unintended effects which are not related to the chemical content of riot control munitions per se include impact injuries causing penetrating trauma, which can be exacerbated by the presence of the chemicals in use. It has been documented that a number of individuals have been struck at close range or in sensitive areas of the body with weapon-fired RCAs such as grenades, cartridges, and other specially designed projectiles causing blindness, other serious injury or death.See, e.g., Hu, H et al (1989) (op. cit.), Ijames, S (2007) Tragedy in Boston: The Impact Projectile Death of Victoria Snelgrove, PoliceOne, December 1st, 2007, Law, B (2013) Bahraini Dies after Being Stuck by Tear Gas Canister, BBC News Online, February 22nd 2013, Sollom, R et al (2012) Weaponizing Tear Gas: Bahrain’s Unprecedented Use of Toxic Chemical Agents against Civilians, Physicians for Human Rights.

While some studies have found no long-term physical effects resulting from single or controlled exposures to CS gas or OC,See, e.g., Karagama, YG (2003) Short Term & Long Term Physical Effects of Exposure to CS Spray, Journal of the Royal Society of Medicine, 2003, Vol. 96(4), and M. Vesaluoma et al. (2000) Effects of Oleoresin Capsicum Pepper Spray on Human Corneal Morphology and Sensitivity, Investigative Ophthalmology and Visual Science, 2000 41(8). longer term effects of exposure to high concentrations of RCAs and/or multiple and repeated exposures over a long period of time is less clear and more concerning.

Research from the Occupied Palestinian Territories in the 1980s, the Republic of Korea in 1987, and Bahrain in 2011–12, indicate that exposure to high concentrations of RCAs and/or exposure over a long period of time can potentially be linked to increases in miscarriage, still-births, and other reproductive anomalies; an apparent rise in asthma rates, respiratory failure, and deterioration in lung function; and that they have the potential to cause long-term carcinogenic effects.L. F. Chasseaud et al. (1975) Suppression of Sebaceous Gland Non-Specific Esterase Activity by Electrophilicaβ-Unsaturated Compounds in Sollom, R et al (2012) (op. cit.), Hu, H et al (1989) (op. cit.), Physicians for Human Rights (unknown); The Casualties of Conflict in Sollom, R et al (2012) (op. cit.), Sollom, R et al (2012) (op. cit.).

There are a number of concerns surrounding specific uses of RCAs.

The use of expired RCAs

In recent years, photographic evidence indicates that expired RCAs have been used in Bahrain (2012), Egypt (2011), India (2012), the Occupied Palestinian Territories (2011), Turkey (2013) and Venezuela (2009).Brown Moses (2013) Imgur Collection, Elsadeq, K (2011) via Twitter, Omega Research Foundation Archives (2009), Proud to be an Indian (2012) via Facebook, STR/Getty (2012) Getty Image ID: 143178781, Wadi Hilweh Information Center (2011) Israel using Expired Tear Gas on Palestinians of East Jerusalem (with pictures).

Generally, RCAs have a shelf life of three to five years, after which they should not be used. The US company Federal Laboratories, in its pamphlet entitled ‘Riot Control’, stresses that inappropriate storage of their RCAs and/or use after the recommended five year shelf life can cause the equipment to malfunction. It states that while out-of-date material should not be used for riot control, they can be used as training aids as ‘in practice sessions it is of no great importance if a device should malfunction’.Federal Laboratories (date unknown) Riot Control, Federal Laboratories. However, little research has been conducted into how the potency of the irritant is affected over time which leads to further concerns (such as on the health of those exposed to the chemical) in addition to the risk of the device malfunctioning.

The use of RCAs in confined spaces

The use of RCAs in confined spaces with limited ventilation is inherently risky and can lead to injury or death through suffocation, allergic reaction or hazardous overdose. RCAs should never be used in confined spaces, or in a place where there is no opportunity for the target to easily escape the effects of the RCA such as in a stadium or a narrow street or alleyway.

The indiscriminate nature of some dispersal techniques

Some RCA dispersal systems available on the market today appear to be, by their very nature, indiscriminate. Water cannons with separate RCA tanks, hand-thrown or weapon-fired grenades and cartridges, and larger sprayer systems, are not targetable to any one individual and as such can affect innocent bystanders. Use of small targetable sprays helps to minimize the risk of excessive amounts being used and of bystanders being affected.

The use of RCAs on already-restrained individuals

RCAs should never be used on an already-restrained individual and never in conjunction with spit hoods or masks as this increases the risk of death or serious injury through allergic reaction, suffocation or positional asphyxia, among others.Spit hoods/masks are placed over the head and mouth of an individual and are designed to prevent the wearing spitting. If used in conjunction with chemical irritants they increase the risk of suffocation by prolonging the closeness of the chemical to the nose and mouth and thus preventing the wearer escaping the effects.

Use of RCAs with electric-shock weapons

Some RCAs contain flammable propellants and should therefore not be used alongside electric shock weapons (such as Tasers) or where there is a fire risk.

Use of RCAs on those with underlying health issues and/or under the influence of drugs or alcohol

Research indicates that some population groups are more likely to be affected by RCAs, for example, those with underlying heath issues such as asthma or hypertension and those who take cocaine;Department of Health (1999) 1999 Annual Report of the Committees on Toxicity Mutagenicity Carcinogenicity of Chemicals in Food, Consumer Products and the Environment, and J. Mendelson et al. (2010) Capsaicin, an Active Ingredient in Pepper Sprays, Increases Lethality of Cocaine, Forensic Toxicology, January 2010, Vol. 28 (1), pp. 33-7. further, ‘the use of [CS] spray in the context of alcohol, drugs and mental illness remains unchartered territory, where the risk is not fully known’ and as such should be used with caution.The Police Complaints Authority (2000) CS Spray: Increasing Public Safety? A Report by the Police Complaints Authority.

Last updated on: 20 July 2017