An article from Do or Die Issue 7. In the paper edition, this article appears on page(s) 135.
CS is an abbreviation for O-chlorobenzylidene malonontrite. The properties of this compound were first discovered by American chemists in 1928, and the potential chemical warfare uses were suggested by a Dutch writer in 1934. During World War Two scientists in various countries studied the effects of the compound but it wasn't seriously developed as a weapon until the mid 1950's. The first widespread use of it was during the Vietnam War and since then it has remained a weapon in the arsenal of armies and police forces the world over.
The canisters that are carried by the police in the UK contain three ingredients: the active chemical (CS), a liquid solvent to dissolve and carry it, and an inert gas to act as a propellant for the spray. The active ingredient, CS, is one of a group of chemical compounds called lachrymators. These chemicals are tear producing agents, hence the euphemism 'tear gas'. Exposure to them causes severe eye irritation, a profuse flow of tears, skin irritation (especially on moist areas of the body) and irritation of the upper respiratory tract, causing sneezing, coughing and difficulty in breathing.
The obvious thing is to wear a gas mask and they are available, although expensive. (The only ones worth using are current military or police designs - don't try any old ones you may come across in markets or army surplus stores as many used asbestos in the filters!)
A mask and hood offer limited protection and of course they are well worth wearing for disguise anyway. An improvement on the normal cloth mask is a special cycle mask as they contain activated charcoal which will filter out some of the CS.
Goggles are useful for eye protection and are easy to get hold of and carry.
Carry a bottle of solution made up from water and sodium metabisulphate (sold as Campden tablets used in home brewing) as this combination neutralises the effects of CS. If you cannot get this use clean water to rinse the eyes and skin affected.
If you are asthmatic tell the people around you before the action starts, so that if when sprayed you have a bad reaction they'll be able to act appropriately by giving you your medication or getting a doctor.
If you are in the line of spray move backwards out of range rather than sideways where the spray may still be able to reach you. If you are in a building move outside. Your eyesight may become blurred and it is easy to lose awareness of what is going on. Do not run blindly into the arms of the police, or worse still, into traffic. Act calmly and stay aware of your surroundings whilst moving to a safe area.
If possible stand upwind of where the spraying happened and expose the affected part of your body to the wind. This will help disperse the gas quickly.
Flush the affected area of the body with the solution mentioned earlier - or just water if this is not available. Do not touch it as you will spread the chemical around and rub it into your pores. It may be possible that you can rejoin the action right away, as small amounts should only affect you for a few minutes.
When possible have a cold/lukewarm shower (hot water opens the pores and allows gas particles in) as soon as possible. Showers flush the chemical away whilst a bath will just re-distribute it.
After the action you should hang your clothes up in a well ventilated area to disperse the last remnants of the gas. When they have hung for a day or so wash them twice - firstly in cold and then secondly in hot water - and they'll be okay to wear again.
CS Gas is fat soluble so never coat your skin in petroleum jelly or similar substances for protection as some people have tried. When sprayed do not treat the area with any cream, jelly or ointment, unless advised to by someone who knows what they are talking about. The best treatments are air, cold water and time.