CS powder (o-chlorobenzylidene malononitrile)，[(2-chlorophenyl)methylene]malononitrile is used primarily as an incapacitating agent, both by military & law enforcement personnel. It can be disseminated in burning grenades & weapon-fired projectiles, as an aerosol from the finely divided solid chemical, or from a solution of the chemical dissolved in methylene chloride or acetone.
CS is used in spray form by many police forces as a temporary incapacitant and to subdue attackers or persons who are violently aggressive. Officers who are trained in the use and application of CS spray are routinely exposed to it as part of their training.
Blank pistol cartridges carrying CS in powder form have been released to the public. These, when fired at relatively close ranges, fully expose the target to the effects of CS, and are employed as a potent defensive weapon in regions where blank firing pistols are legally permitted for such use.
Although predominantly used by police it has also been used in criminal attacks in various countries.
Use of CS in war is prohibited under the terms of the Chemical Weapons Convention, signed by most nations in 1993 with all but five other nations signing between 1994 and 1997. The reasoning behind the prohibition is pragmatic: use of CS by one combatant could easily trigger retaliation with much more toxic chemical weapons such as nerve agents. Only four nations have not signed the Chemical Weapons Convention and are therefore unhindered by restrictions on the use of CS gas.
Domestic police use of CS is legal in many countries, as the Chemical Weapons Convention prohibits only military use.