Nerve gas1 actually refers to a collection of different compounds that act in a similar manner to disrupt the nervous system. The “G” class of nerve gases are organophosphates and it is the phosphorous group that is so important in the poisonous activity of nerve gas. Originally produced during World War II but never used at that time, these compounds are a more contemporary threat since they have been used in modern times during wars and terrorist acts. The most common nerve gases in the “G” class are sarin, tabun and soman (Figure 1). These compounds are colorless and odorless gases and are extremely toxic; a small droplet can kill a person. They exist in both liquid and gaseous forms. Inside closed containers, the nerve gases are in liquid form, but since they have a very high vapor pressure at room temperature, they vaporize when exposed to air. The vapor is 4 times as dense as (heavier) air so it hovers close to the ground where it is more likely to come in contact with humans and animals.
1 a group of very lipophilic compounds (e.g. sarin, tabun, soman) that can exist as a vapor at room temperature. They contain phosphorus groups and bind avidly to acetylcholinesterase to inhibit its activity. The inhibition of acetylcholinesterase causes the accumulation of acetylcholine in all areas of the nervous system, causing excessive muscle contraction followed by paralysis, secretions, seizures and death by respiratory failure.