CS gas: general information
Updated 16 November 2022
© Crown copyright 2022
This publication is licensed under the terms of the Open Government Licence v3.0 except where otherwise stated. To view this licence, visit nationalarchives.gov.uk/doc/open-government-licence/version/3 or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: psi@nationalarchives.gov.uk.
Where we have identified any third party copyright information you will need to obtain permission from the copyright holders concerned.
This publication is available at https://www.gov.uk/government/publications/cs-gas-incident-management/cs-gas-general-information
Overview
2-chlorobenzylidene malononitrole or ‘CS’:
- is a synthetic (man-made) chemical
- is a white crystalline solid when pure
- is an irritant and exposure causes burning sensation in the eyes and tearing
- can be used in a liquid or gaseous form to temporarily incapacitate individuals or groups
Uses of CS gas
The substance causes irritation in humans and is used by UK police forces as a temporary incapacitant spray to subdue persons who pose a risk to themselves and/or the police officers and others in the vicinity. It may be dispersed in a smoke cloud or dissolved into liquid (the solvent methyl iso-butyl ketone) to be used as a spray. The CS spray carried by some UK police forces contains 5% 2-chlorobenzylidene malononitrole. It is also used by the military in training operations and for testing gas masks.
These substances may be referred to as CS or tear spray or gas (not to be confused with PAVA spray which is also referred to as tear spray or gas). In this document, the use of the term ‘CS gas’ is used to refer to any gasses or sprays containing 2-chlorobenzylidene malononitrole.
How CS gas gets into the environment
CS gas may be released during its use, or following an accident during storage, transport or disposal. When released, CS gas will disperse into the atmosphere in a matter of minutes.
Exposure to CS gas
CS gas is released into the air via an aerosol spray or in smoke. Exposure may occur by skin or eye contact or by breathing in the gas.
How exposure to CS gas can affect your health
Exposure to CS gas can be by breathing it or by skin and eye contact with it; however, the general public are unlikely to be exposed to CS gas. Following exposure to any chemical, the adverse health effects you may encounter depend on several factors, including the amount to which you are exposed (dose), the way you are exposed, the duration of exposure, the form of the chemical and if you were exposed to any other chemicals.
Exposure to CS gas may cause intense tear production, eye pain, chest tightness, coughing and sneezing. If ingested, a stinging or burning sensation in the mouth with increased salivation and vomiting may occur. Contact with the skin will lead to burning and stinging with possible redness and blistering. Treatment is rarely needed because people usually recover quickly (within 15 to 30 minutes) after a brief exposure. Redness of the eyes and skin may last for a few hours after exposure.
Exposure to large amounts of CS gas (such as that following release of CS gas in a confined space) for a long time may result in lung damage. Physical injury to the eyes may occur if CS gas is sprayed directly into them at a very close range.
CS gas and cancer
CS gas is not thought to cause cancer in humans.
Vulnerable people
People with breathing difficulties such as asthma may be more sensitive to the effects of CS gas. This is because CS gas can cause irritation of the airways leading to cough and shortness of breath.
Pregnancy and the unborn child
The limited available data suggests that exposure to CS gas following its use by police forces is not associated with harm to the unborn child.
Children
The effect of CS gas on children is likely to be the same as for adults.
What to do if you are exposed to CS gas
Initial advice following exposure to CS gas
You should remove yourself from any confined space. CS gas will disperse in fresh air in a few minutes. Complete recovery should be rapid (15 to 30 minutes). Do not rub your eyes as this may make symptoms worse. Do not wash the skin as using water immediately after exposure may make symptoms worse by spreading CS around the body.
If symptoms persist for longer than 30 minutes
If you have got CS gas on your skin, remove soiled clothing (not over the head) and seal in plastic bags. Exposed skin should be blotted and wiped with any available dry, absorbent material like paper tissue, towels, etc. Do not blot or wipe aggressively. Avoid moving contamination from one part of the body to another. Seek medical advice.
If you have got CS gas in your eyes, remove contact lenses, irrigate the affected eye with lukewarm water for at least 10 to 15 minutes and seek medical advice.
If you have got CS gas in your eyes or have inhaled CS gas and symptoms persist for longer than 30 minutes, seek medical advice.
Additional sources of information
NHS.UK has more information on poisoning.
The information contained in this document from the UKHSA Radiation, Chemicals and Environment Directorate is correct at the time of its publication.
Email chemcompendium@phe.gov.uk or enquiries@ukhsa.gov.uk if you have any questions about this guidance.