djm@castle.ed.ac.uk (D Murphy) (08/28/90)
From: D Murphy <djm@castle.ed.ac.uk> I suppose I'd better add this for completeness... Given that you know what chemical warfare agents are, how they work and how to stop people affected by them dying, how do you actually protect personnel against a chemical threat ? That depends on what is being used. In the case of hydrogen cyanide (or chlorine gas), skin contact is not a major method of uptake of the poison into the body. Inhalation is - and with chlorine so is severe irritation of the eyes. In this case respirators equipped with carbon or other filters capable of destroying the agent are sufficient - hydrogen cyanide can be destroyed by oxidising agents, and chlorine by a variety of materials as it is very reactive - especially during the daylight hours. Blister agents which attack the skin and throat/lung linings, and nerve agents which are absorbed by the skin must be kept away from the body. Such environmental insulation can be provided by rubbers or polymers designed to resist the corrosive action of blister agents (neoprenes etc) and are used for the bodies of gloves and respirators. The trouble with these materials is that they are also impermeable to water and so are just about impossible to wear (I've heard that Warsaw Pact CBW suits are pretty much all rubber). However, carbon as charcoal and similar forms is a very good chemical adsorbent - it also has a very high surface area/weight for this adsorption to occur on. Organic molecules such as nerve or blister agents will be adsorbed onto the surface of the carbon, and neutralising agents incorporated into the adsorbent will destroy the chemical before it is re-released from the surface (this chemical adsorption is a dynamic, and therefore reversible process). The carbon can be contained between two layers of cloth - typically cotton for its wearing properties (as I believe the US suits have), or be incorporated into the cloth itself (as the UK suits use). This allows some passage of air/water vapour through the suit - although it is restricted and as has been pointed out compromises combat efficacy. Aircraft and small naval ships can be decontaminated with hoses to dilute the hazard. Larger naval vessels carry sprinkler systems for this purpose (I have a photo of HMS Invincible washing off her flight deck - beats the hell out of a rating with a brush :-). Decontamination can be either via dilution or, where this is impractical (for instance in the desert) by using either neutralising materials (bleach for cyanides, just about anything for blister agents, and alkali for nerve agents) or powder adsorbents such as silica or talc which remove the agent into themselves and can then be disposed of safely. Murff...