Chemical weapons: Choking agents

Chemical weapons: Choking agents

Russian soldiers prepare to deal with what they think is phosgene

BBC News Online looks at the effects and use of choking gases such as phosgene and chlorine.

Main agents: Phosgene, chlorine

Effects: Agents enter the body through inhalation, choking the victim by causing fluid to build up in the lungs. Phosgene gas can take up to 48 hours to affect a victim, unlike the weaker chlorine gas which affects people almost immediately.

Recognition: Yellow-green gas, smelling of swimming pools or newly-mown hay.

Use as a weapon: Early attacks relied on gas cylinders being opened or on placing the gas in artillery shells.

History: Chlorine gas was used in World War I by both the Germans the British. The Russian military has also claimed that it has been used in Chechnya.

Production: Phosgene is widely-used in civilian industries, such as the manufacture of dyes, pharmaceuticals, herbicides and insecticides, while chlorine is used to purify water. Both are therefore widely available.

Protection: Gas masks