UXO 101  Riot Control Agents CS and CN

The military uses riot control agent filled munitions including grenades and projectiles for tactical purposes such as flushing enemy from bunkers and tunnels. Two such riot control agent fillers are Chloracetophenone commonly called CN and Orthochlorobenzylidene Malononitrile commonly called CS. CN and CS agents are considered irritants and are often referred to as "Tear Gas".

CN dates back to 1869 when it was first discovered by a German chemist. CN is a yellowish brown solid substance that has a melting point of 54°C. When it burns it produces a white smoke that in minute quantities has an apple blossom odor. CN is poorly soluble in water but dissolves in organic solvents. Exposure to CN primarily affects the eyes by producing a burning sensation. Exposure to high concentrations of CN can cause irritation of the upper respiratory tract and inflammation of the skin. Ingestion of food or water contaminated with CN causes nausea and vomiting. After about 1 or 2 hours all symptoms disappear.

To view an engineering sketch created in the 1930s when the CN hand grenade was developed use the download link below. The sketch came from the National Archives. A picture of a M7A1 CN filled hand grenade is shown below.

CS is also riot control agent and has basically superseded CN in training scenarios because it produces a greater irritant effect and is much less toxic. It was discovered and developed by B.B. Corson and R.W. Stoughton in 1920s. CS is available in two forms for field use: persistent and non-persistent. Persistent CS comes in a fine powder form that is normally released from bursting munitions. Persistent CS is used to deny areas to enemy use as the CS powder remains active in the target area for a period of several weeks. Use of the area by the enemy stirs the powder back into the air thus forcing him to withdraw. Examples of persistent CS munitions are: CS drums (dropped from CH-47 helicopters), and field expedient CS bunker bombs. The M-25A2 grenade is technically a CS persistent munition, but because of the small amount of CS in each grenade, it is not used for area denial purposes.

Non-persistent or tactical CS is dispersed into the air from burning munitions. It is used to incapacitate the enemy present at that time. After the agent cloud is dispersed by surface winds no residual contamination remains. Examples of non-persistent CS munitions are the E-158 canister clusters (dropped from UH-1 aircraft), E-8 tactical CS launchers (ground or vehicular mounted), XM-629 105mm CS rounds, XM-651 40mm CS rounds (fired from M-79 grenade launchers), XM-630 4.2in CS rounds and M-743 grenades.

CS is also poorly soluble in water but dissolves in organic solvents. When dispersed, the CS cloud is white at the point of release and lasts for several seconds. Exposure to CS is associated with a pepper-like odor. The irritant produces a burning sensation in the eyes as well as dyspnoea (difficulty breathing), coughing and rhinorrhoea (runny nose).

Sources:

Army Field Manual (FM) 8-9 "NATO HANDBOOK ON THE MEDICAL ASPECTS OF NBC DEFENSIVE OPERATIONS"

Department of the Army Headquarters, 25th Infantry Division Memo dated Aug 1970. Letter of Instructions 23-70 Employment of Riot Control Agent