World Health Organization
منظمة الصحة العالمية
Organisation mondiale de la Santé

Nerve gases: Tabun (CAS 77-81-6); Sarin (CAS 107-44-8); Soman (CAS 96-64-0); VX (CAS 50782-69-9) fact sheet


The designation “nerve gas” or “nerve agent” is used for organophosphorus compounds that inhibit tissue cholinesterase. It is an allusion to the mode of action of these substances, namely the disruption of nerve impulse transmission.

At the present time, two families of nerve gases are important for military purposes, namely the G agents, which are alkyl esters of methylphosphonofluoridic acid or of dialkylphosphoramidocyanidic acid, and the V agents, which are mainly alkyl esters of S‐dialkylaminoethyl methylphosphonothiolic acid.

G agents (e.g. sarin, tabun and soman) are primarily designed to act via inhalation, while V agents (eg. VX) act primarily through skin penetration and by inhalation of aerosol. Chemically and toxicologically, the nerve gases are similar to many of the commercial organophosphate pesticides and, while information on severe nerve gas poisoning in humans is rather limited, there are extensive data on human exposure to some of these pesticides.

Nerve agents are mostly odourless and colourless to yellow‐brown liquids at ambient temperature, and are soluble in water except V agents. Nerve agents are heavier than air and will tend to accumulate in low-lying areas.

Latency period

The effect of exposure to sarin depends on the amount of the agent, route and duration of the exposure. The symptoms will appear within a few seconds after inhalation exposure to the vapor form and from a few minutes to 18 hours after exposure to the liquid form.

Main clinical signs and symptoms
Following local exposure
Following systemic absorption
Principles of medical management

Tabun, sarin and soman are quite volatile and are considered to have low environmental persistence, whereas thickened soman and VX may persist in the environment for days, depending on temperature and other environmental conditions; generally persistence is prolonged at low temperatures.  

Decontamination procedures for skin, equipment and materiel have been developed by most armies, using neutralizing, active chemicals, such as chloramine solutions, or neutral adsorbing powders, e.g. fuller’s earth.

How to protect yourself

Recovery from nerve gases or agents exposure is possible with treatment, but the antidotes available must be used quickly to be effective. Therefore, the best thing to do is avoid exposure:

Removing and disposing of clothing
Washing the body

Chemical protective clothing containing activated carbon layer and a full-face gas mask with an appropriate filter should be used.   


Medical Management of Chemical Casualties Handbook, 4th ed 2007. US Army Medical Research Institute of Chemical Defense [pdf 102Mb]

Medical Management Guidelines for Nerve Agents [pdf 289.5kb]

Public health response to biological and chemical weapons—WHO guidance (2004)

Quick Reference Guides (Sarin, Soman, Tabun, VX) (2011) US National Response Team