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|Molar mass||195.22 g/mol|
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
CR gas or dibenzoxazepine, or its chemical name dibenz[b,f][1,4]oxazepine, is an incapacitating agent and a lachrymatory agent. CR was developed by the British Ministry of Defence as a riot control agent in the late 1950s and early 1960s.
CR is a pale yellow crystalline solid with a pepper-like odor. It is slightly soluble in water and does not degrade in it. CR is usually presented as a microparticulate solid, in the form of suspension in a propylene glycol-based liquid. Contrary to its common name, it is not a gas but a solid at room temperature.
These gases are usually fired in canisters (LACR) that heat up, producing an aerosol cloud at a steady rate.
CR gas is a lachrymatory agent (LA), exerting its effects through activation of the TRPA1 channel. Its effects are approximately 6 to 10 times more powerful than those of CS gas. CR causes intense skin irritation, in particular around moist areas; blepharospasm, causing temporary blindness; and coughing, gasping for breath, and panic. It is capable of causing immediate incapacitation. It is a suspected carcinogen. It is toxic, but less so than CS gas, by ingestion and exposure. However, it can be lethal in large quantities. In a poorly ventilated space, an individual may inhale a lethal dose within minutes. Death is caused by asphyxiation and pulmonary edema.
The effect of CR is long-term and persistent. CR can persist on surfaces, especially porous ones, for up to 60 days.
While CS can be decontaminated with a large amount of water, use of water may exacerbate the effects of CR. Skin contaminated with CR gas may become extremely painful in contact with water for up to 48 hours after contamination.
During the protests against the military government in Egypt, Egyptian security forces allegedly used CR gas in addition to the more commonly-used, less debilitating CS gas. One protester described the gas as making him feel "as if your eyes are about to fall out; then you have trouble breathing, and you lose your sight" Egyptians used yeast as a treatment for CR side effects on skin. Mohammed ElBaradei also confirmed via Twitter that "tear gas with [a] nerve agent" is being used in Tahrir Square.
The only gas that has been identified by human rights organizations in protests "is CS tear gas, typically used by police forces to disperse crowds," stated Egyptian journalist Farida Helmy.  Alleged use of CR gas, which is six times more powerful than CS, has not been corroborated according to Human Rights Watch (HRW).
Israel Police forces spray CR gas at riot control situations. It is widely used at demonstrations within the Palestinian citizens and at the Israeli West Bank barrier.
CR tear gas was used in suppression of the mutiny in Makati that was led by Sen. Antonio Trillanes. The tear gas was fired in the building and all the people in the building including reporters were affected.
The LTTE, also known as Tamil Tigers of Sri Lanka, an insurgent group in Sri Lanka used CR gas against government forces that were on an offensive to flush and defeat these insurgents during September 2008. Its use hindered the army's progress but ultimately proved ineffective in preventing the army from overrunning LTTE positions. This is one of the first few cases of insurgents using CR gas as an insurgent weapon.
At Ukraine, CR gas is commonly used by special forces against demonstrators. Gas is packed in a form of spray cans "Cobra 1". For example, gas has been used on demonstration dedicated to Ukraine Independence Day (Aug 24 2011). Also massive gas usage has been documented during demonstrations against Language Law Draft at Kiev on Jul 3-4 2012.
It has been reported that thousands of tons of CR gas were used by the U.S. forces in Vietnam to bring Viet Cong into the open. It was also used by the North Vietnamese forces in some battles like Hue in 1968 or during the Easter Offensive in 1972.
Republican groups in Northern Ireland have alleged that British Army and Royal Ulster Constabulary units used CR gas against Republican prisoners in the 1970s.
CR tear gas was used at the G8 protests in Genoa, Italy and Quebec City, Canada during the FTAA anti-globalization demonstrations during the Quebec City Summit of the Americas.
The Canadian, Norwegian, and Australian Armies train their soldiers with CR gas in a manner similar to that of the USA, as it is a basic part of CBRN (Chemical, Biological, Radiological, Nuclear) training. Gas is released by burning tablets, usually in a building reserved for this purpose (a "gas hut"). In the training, the person enters the building unprotected, and must fit and clear the gas mask before leaving. Other drills such as drinking and under-mask decontamination are also practiced. Some Norwegian units are exposed to CR-gas while engaged in physical activity such as push-ups.
Because of its alleged carcinogenic properties, the United States does not utilize CR for riot control. The U.S. military classification for this chemical agent is combat class chemical weapon causing serious side-effects for humans.
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- Gijsen HJ, Berthelot D, Zaja M, Brône B, Geuens I, Mercken M (October 2010). "Analogues of Morphanthridine and the Tear Gas Dibenz[b,f][1,4]oxazepine (CR) as Extremely Potent Activators of the Human Transient Receptor Potential Ankyrin 1 (TRPA1) Channel". J Med Chem 53 (19): 7011–7020. doi:10.1021/jm100477n. PMID 20806939.
- "Tear Gases: CR - Dibenzoxazepine". Zarc International, Inc. Retrieved November 22, 2011.
- "Beskylder egyptiske styrker for massakre" (in Norwegian). NRK.no. Retrieved November 22, 2011.
- Farida Helmy, "Chemical Combat", Egypt Today Magazine, January 2012 issue
- http://inac.org/action/alert/134[dead link]
- Olajos EJ, Salem H (2001). "Riot Control Agents: Pharmacology, Toxicology, Biochemistry and Chemistry". J Appl Toxicol 21 (5): 355–391. doi:10.1002/jat.767. PMID 11746179.
- "Ireland, Organise! Press Release -Less Lethal Weapons Action Belfast". A-Infos. Retrieved November 22, 2011.
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