Providing Protection In Hazardous Environments

Dr Matt Chinn, Technical Manager Protection & Decontamination, Defence Science & Technology Laboratory, Porton Down, on 26 April 2002

This Laboratory was established in 1916 on a 7000-acre site in Wiltshire, and now has approximately 850 employees. The majority of the site has been untouched by agriculture since 1916 and as a result of the diverse range of flora and fauna is a designated Special Site of Scientific Interest. The Laboratory carries out work on Hazard Assessment; Detection (many of the agents are colourless and odourless); Protection & Decontamination (which means protecting lungs and skin of people in the open, in vehicles and in buildings); Medical Countermeasures (e.g. vaccines); and Demilitarisation (including destruction of previously stockpiled weapons). Many countries have similar establishments to protect their own citizens, and some specialise in particular aspects for the benefit of their alliances. This talk described the hazards, the history of protection, and the developments in equipment.

There are a range of hazardous materials of increasing potency ranging from those used in industrial processes such as hydrogen cyanide and phosgene to agents of biological origin such as anthrax, plague and smallpox. The least hazardous materials include hydrogen cyanide (HCN or Prussic Acid), a poison everyone has met in crime stories as quick fatal and very dangerous. The worst materials are rated as 109 (1 thousand million times) more hazardous! Chemical agents of concern include the following:

Choking / blood agents (e.g. Chlorine and HCN)
Blister agents (e.g. mustard gas)
Nerve agents (e.g. Sarin)
Tear gases (e.g. CS gas)

Many of the chemical agents have civilian uses as feedstock for dyes, drugs and other industrial products. The first protective mask known was that used in the 1500s against plague; and the first patent was in the US in 1849 to P. Haslett.

In warfare, chlorine was used at the Battle of Ypres in April 1915 when 168 tonnes was discharged from cylinders by the Germans. It blew gently across the ground like a mist and breathing it caused choking, followed by death as the lungs filled with fluid.

Medieval plague mask

The masks devised to prevent it being breathed in consisted of hoods tucked into the collars of jackets, initially impregnated with urea (replenished in the field with urine) and subsequently with various chemicals.

Improved gas masks were quickly developed incorporating charcoal impregnated with sodium permanganate, and later using activated carbon. Activated carbon is capable of adsorbing many gases on to its surface.

Impregnating it with copper, silver and chromium salts makes it more effective against particular gases and vapours. The active carbon is contained in a canister that also has a filter to remove particles, such as smoke. The gas masks issued to civilians during World War II were of this type.

This type of face mask can leak because it does not fit round the face tightly. For soldiers active on the field of battle there is a need for a better fitting mask, which they can wear comfortably for a long time. They also have to be able to see well out of it, communicate and, in hot climates, drink.

It must protect them for long periods without breathing becoming restricted, and the canister must last a long time before it is saturated and has to be changed. A series of masks has been developed and the latest meets all these requirements. It is also necessary to provide protective clothing since blister agents, as the name implies, damage the skin. Methods of treating fabrics and fastenings (zips, etc.) to repel liquids have been developed but the rough use to which army uniforms are put means extensive testing on a moving body has to be carried out. This can either be done with a live person and using harmless simulant materials such as sodium chloride or with a dummy and the actual hazardous chemicals, which is DSTL's procedure. `Portonman' (a robot) walks vigorously for 12 hours in an atmosphere-controlled chamber and is fitted with patches and dosimeters to detect any chemicals that have penetrated the suit.

However, a soldier needs to be able to remove even the latest suit and rest in a safe area. Vehicles and buildings, which are air-conditioned using regenerative chemical absorbers to remove hazardous materials from the incoming air, are used, together with an over-pressure inside the building, like present clean rooms in some manufacturing plants.

DSTL co-operates with similar laboratories in NATO and allied countries. Their remit is to protect the military forces but they are also called upon to inform the Home Office of equipment suitable for civilian use.

Donald Lovell