Pepper spray, also known as OC spray (from "Oleoresin Capsicum"), OC gas, and capsicum spray, is a lachrymatory agent (a chemical compound that irritates the eyes to cause tears, pain, and even temporary blindness) that is used in riot control, crowd control, and personal self-defense, including defense against dogs and bears.
Although considered a less lethal agent, it may be deadly in rare cases, and concerns have been raised about a number of deaths where being pepper sprayed may have been a contributing factor.
The active ingredient in pepper spray is capsaicin, which is a chemical derived from the fruit of plants in the Capsicum genus, including chilis. Extraction of oleoresin capsicum from peppers involves finely ground capsicum, from which capsaicin is extracted in an organic solvent such as ethanol. The solvent is then evaporated, and the remaining waxlike resin is the oleoresin capsicum. An emulsifier such as propylene glycol is used to suspend the OC in water, and pressurized to make it aerosol in pepper spray. The high performance liquid chromatography (HPLC) method is used to measure the amount of capsaicin within pepper sprays. Scoville Heat Units (SHU) are used to measure the concentration or "heat" of pepper spray.
A synthetic analogue of capsaicin, pelargonic acid vanillylamide (desmethyldihydrocapsaicin), is used in another version of pepper spray known as PAVA spray which is used in the United Kingdom. Another synthetic counterpart of pepper spray, pelargonic acid morpholide, was developed and is widely used in Russia. Its effectiveness compared to natural pepper spray is unclear.
Pepper spray typically comes in canisters, which are often small enough to be carried or concealed in a pocket or purse. Pepper spray can also be bought concealed in items such as rings. There are also pepper spray projectiles available, which can be fired from a paintball gun. It has been used for years against demonstrators.
Pepper spray is an inflammatory. It causes immediate closing of the eyes, difficulty breathing, runny nose, and coughing. The duration of its effects depend on the strength of the spray but the average full effect lasts around thirty to forty-five minutes, with diminished effects lasting for hours.
The Journal of Investigative Ophthalmology and Visual Science published a study that concluded that single exposure of the eye to OC is harmless, but repeated exposure can result in long-lasting changes in corneal sensitivity. They found no lasting decrease in visual acuity.
The European Parliament Scientific and Technological Options Assessment (STOA) published in 1998 “An Appraisal of Technologies of Political Control” with extensive information on pepper spray and tear gas. They write:
For those with asthma, taking other drugs, or subject to restraining techniques which restrict the breathing passages, there is a risk of death. The Los Angeles Times has reported at least 61 deaths associated with police use of pepper spray since 1990 in the USA,. The American Civil Liberties Union (ACLU) documented 27 people in police custody who died after exposure to pepper spray in California since 1993. However, the ACLU report counts any death occurring within hours of exposure to pepper spray. In all 27 cases, the coroners' report listed other factors as the primary cause of death, though in some cases the use of pepper spray may have been a contributing factor.
The US Army concluded in a 1993 Aberdeen Proving Ground study that pepper spray could cause "Mutagenic effects, carcinogenic effects, sensitization, cardiovascular and pulmonary toxicity, neurotoxicity, as well as possible human fatalities. There is a risk in using this product on a large and varied population". However, the pepper spray was widely approved in the US despite the reservations of the US military scientists after it passed FBI tests in 1991. As of 1999, it was in use by more than 2000 public safety agencies.
The head of the FBI's Less-Than-Lethal Weapons Program at the time of the 1991 study, Special Agent Thomas W. W. Ward, was fired by the FBI and was sentenced to 2 months in prison for receiving payments from a peppergas manufacturer while conducting and authoring the FBI study that eventually approved pepper spray for FBI use. Prosecutors said that from December 1989 through 1990, Ward received about $5,000 a month for a total of $57,500, from Luckey Police Products, a Fort Lauderdale, Florida-based company that was a major producer and supplier of pepper spray. The payments were paid through a Florida company owned by Ward's wife.
Like Tasers, pepper spray has been associated with positional asphyxiation of individuals in police custody. There is much debate over the actual "cause" of death in these cases. There have been few controlled clinical studies of the human health effects of pepper spray marketed for police use, and those studies are contradictory. Some studies have found no harmful effects beyond the effects described above.
Direct close-range spray can cause more serious eye irritation by attacking the cornea with a concentrated stream of liquid (the so-called "hydraulic needle" effect). Some brands have addressed this problem by means of an elliptically cone shaped spray pattern.
Capsaicin is not soluble in water, and even large volumes of water will not wash it off. Victims are generally encouraged to blink vigorously in order to encourage tears, which will help flush the irritant from the eyes.
A formal study of five often-recommended treatments for skin pain (Maalox, 2% lidocaine gel, baby shampoo, milk, or water) concluded that:
To avoid rubbing the spray into the skin, thereby prolonging the burning sensation, and in order to not spread the compound to other parts of the body, victims should try to avoid touching affected areas. There are also wipes, manufactured for the express purpose of serving to decontaminate someone who has received a dose of pepper spray. Many ambulance services and emergency departments use baby shampoo to remove the spray and with generally good effect. Some of the OC and CS will remain in the respiratory system, but a recovery of vision and the coordination of the eyes can be expected within 7 to 15 minutes.
Some "triple-action" pepper sprays also contain "tear gas" (CS gas), which can be neutralized with sodium metabisulfite (Campden tablets, used in homebrewing), though it, too, is not water soluble and needs to be washed off using the same procedure as for pepper spray.
Pepper spray is banned for use in war by Article I.5 of the Chemical Weapons Convention which bans the use of all riot control agents in warfare whether lethal or non-lethal. In the US, when pepper spray is used in the workplace, OSHA requires a pepper spray MSDS be available to all employees .
In Hong Kong, pepper spray is classified as "arms" under the "Laws of Hong Kong". Chap 238 Firearms and Ammunition Ordinance. Without a valid license from the Hong Kong Police Force, it is a crime to possess and can result in a fine of £100,000 and to imprisonment for 14 years.
In India pepper spray is legal and does not require any license; however they are not sold over the counter and may only be used in self-defense.
In Iran the use of pepper spray is forbidden and is only used by police forces.
In Iraq OC spray is carried by U.S. military guard force members working in detainee operations.
In The Philippines the use of pepper spray for self defense is totally legal, and it is quite freely available in stores.
In South Korea Pepper spray containing OC is legal, however gas-gun types need a simple license to own. CS is only available for police and private security firms.
In the Northern Territory of Australia capsicum spray is prescribed by regulation to be a prohibited weapon under the Weapons Control Act. This legislation makes it an offence for someone without permit, normally anyone who is not an officer of Police/Correctional Services/Customs/Defence, to carry a prohibited weapon.
In Ireland, the police force, (An Garda Síochana, Guardians of the peace), have recently been given pepper spray in an attempt to reduce attacks on its officers, however they remain an unarmed force. Possession of this spray by persons other then Gardaí is an offence under the Firearms and Offensive Weapons Act, as the spray is legally classed as a firearm.
In Belgium it is classified as a prohibited weapon, and it is illegal for anyone other than police officers to carry a capsicum spray. The use by the security services of public transport companies is also authorised after obtaining permission from the minister of internal affairs.
In Denmark possession of pepper spray is illegal for private citizens. As of 2008, police officers carry pepper spray as part of their standard equipment. This was introduced following the shooting of a number of mentally ill citizens – in 2006 also killing 4 people – who had behaved violently or in a threatening manner, leaving the police force in want of a defensive, less-lethal weapon. However, the police have also continued carrying guns, using them as frequently as before, causing the Danish civil liberties organization KRIM to conclude that pepper spray has not displaced the use of guns, but merely added to the arsenal of weapons of the police force.
In Hungary pepper spray is reserved for law enforcement (including civilian members of the auxiliary police), civilians may carry canisters filled with maximum 20 gramms of any other lachrymatory agent. However there is no restriction for pepper gas pistol cartridges.
In Slovakia pepper spray is classified as a self-defense weapon, and it is available to anyone over 18. Use against humans is officially prohibited.
In Finland it is classified as a device governed by the firearm act and possession of pepper spray requires a license. Licenses are issued for defensive purposes and to individuals working jobs where such a device is needed such as the private security sector The Finnish Supreme Court, although, has recently ruled in KKO:2010:7 that owning a pepper spray in self is not a punishable act; but on the other hand, carrying one can be punished as a device capable of harming other people.
In Germany pepper sprays labelled for the purpose of defense against animals may be owned and carried by anyone (even minors). Such sprays are not legally considered as weapons §1. Carrying it at (or on the way to and from) demonstrations may still be punished Sprays that are not labelled "animal-defense spray" or do not bear the test mark of the Materialprüfungsanstalt de:Materialprüfungsanstalt (MPA) (material testing institute) are classified as prohibited weapons. Justified use against humans as self-defense is allowed. CS sprays bearing a test mark of the MPA may be owned and carried by anyone over the age of 14.
In Iceland possession of pepper spray is illegal for private citizens. Police officers carry pepper spray as part of their standard equipment.
In Latvia pepper spray in canisters is classified as a self-defence device and can be bought and carried by anyone over 16 years of age, and pepper spray handguns can be bought and carried without any license by anyone over 18.
In the United Kingdom, "Any weapon of whatever description designed or adapted for the discharge of any noxious liquid, gas or other thing" is a Prohibited Weapon, under S.5 of The Firearms Act 1968. The same act covers other prohibited weapons such as automatic firearms and rocket launchers, all of which can only be possessed by permission of the Home Secretary. Although legal for police officers, recent debates have arisen whether such a weapon should be legal for civilians as means of defensive purposes only. 
In Russia pepper sprays are classified as a self-defence device (not a weapon) and can be carried by anyone over 18. Usage against humans is legal. OC is not only agent used, CS, CR, PAM (МПК) and (rarely) CN are also perfectly legal and highly popular.
In Switzerland pepper sprays are classified as a self-defence device (not a weapon) and can be carried by anyone. Usage against humans is legal.
In Spain approved pepper spray made with 5% CS is available to anyone older than 18 years. Has recently been adopted for some civilian use OC pepper spray (e.g. one of 22 grams, with no registration DGSP-07-22-SDP, approved by the Ministry of Health and Consumption).
In Canada all products with a label containing the words pepper spray, mace, etc, or otherwise originally produced for use on humans are classified as a prohibited weapon. Only law enforcement officers and individuals/corporations who have special government permits may legally carry or possess pepper spray. Any similar canister with the labels reading "dog spray" and/or "bear spray" is regulated under the Pest Control Products Act - while legal to be carried by anyone, it is against the law if its use causes 'a risk of imminent death or serious bodily harm to another person' or harming the environment and carries a penalty up to a fine of $500,000 and jail time of maximum 3 years. Of course, the legality of using spray intended for animal deterrent on a person would be determined in court on a case-by-case basis.