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CR gas

CR gas
IUPAC name dibenz[b,f][1,4]oxazepine
CAS number 257-07-8
Molecular formula C13H9NO
Molar mass 195.22 g/mol
Density g/cm3
Melting point

73 °C

Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

CR gas or dibenzoxazepine, chemically 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.


Physical properties

CR is a pale yellow crystalline solid with a pepper-like odour. 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 actually a gas but is solid at room temperature.

It is chemically related to loxapine, a typical antipsychotic drug. CR is loxapine's parent compound. It was first synthesised in 1962.[1]

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). CR gas is about 6-10 times stronger than CS gas. It causes very intense irritation and skin pain, namely around moist areas, blepharospasm causing temporary blindness, coughing and 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. [2]

Medical treatment is mostly palliative. The contaminated clothing has to be removed. The eyes and skin can be washed, the eye pain can be alleviated with medications.[3]


In the late 1980s, CR was used in the townships in South Africa. It caused some fatalities, particularly among children.[4]

Because of its alleged carcinogenic properties, the United States does not utilize CR for riot control.[5]

  • Military chemical compounds and their properties


  1. CAS-Number and SMILES
  2. ^  Higginbo R, Suschitzky H (1962). "Synthesis of Heterocyclic Compounds .2. Cyclisation of O-Nitrophenyl Oxygen Ethers". J Chem Soc: 2367-2370.
  3. ^
  4. ^ Olajos EJ, Salem H (2001). "Riot Control Agents: Pharmacology, Toxicology, Biochemistry and Chemistry". J Appl Toxicol: 355-391.
  5. ^
  6. ^
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "CR_gas". A list of authors is available in Wikipedia.
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