Building protection
 Threats, biochemical weapons, nerve agents
Toxic chemicals
Chemical Warfare Agents
Like biological agents, chemical agents can be classified in a variety of different ways depending on the
type of characteristic that is of primary concern. A common classification is according to their effect on body.
Typical classes include nerve agents, vesicants, blood agents, lung irritants, sensory irritants and psychotropic
agents. Following are details of main chemical agents.
Nerve Agents
Nerve agents are extremely toxic chemicals that were first developed before and during World War II primarily
for military use. Nerve agents inhibit cholinesterase.
The vapour or aerosol exposure (the product of concentration C and time t) needed to cause death in 50 % of
the exposed population is known as the LCt50 . Since the dose is the product of C·t, a particular value can
be produced by varying the values of C and t. Thus, an effect that is produced by an exposure of 0.5 mg/m3
for 100 minutes is also produced by an exposure to 50 mg/m3 for 1 minute (Ct=50 mg min/m3 in both cases).
The estimated LCt50 s for humans are shown in Table 2. It is seen that the four nerve agents are liquid at normal
temperatures.
Table 2. Chemical, physical and biological properties of nerve agents
| Properties |
Tabun (GA) |
Sarin (GB) |
Soman (GD) |
VX |
| Boiling point(ºC) |
230 |
158 |
198 |
298 |
| Vapour pressure at 20 ºC (Pa) |
4,9 |
280 |
53 |
0,1 |
| Molecular weight |
162 |
140 |
182 |
267 |
| Volatility (mg/m3 at 25 °C) |
610 |
22000 |
3900 |
10,5 |
| Appearance |
Colorless to brown liquid |
Colorless liquid |
Colorless liquid |
Colorless to straw-coloured liquid |
| Odour |
Fairly fruity |
No odour |
Fruity; oil of camphor |
Odorless |
| LCt50 (mg·min/m3) |
400 |
100 |
50 |
10 |
Blister Agents
Blister agents (vesiscant) are agents that produce vesicles or blisters. They were firs used as a chemical
weapon during the First World War.
Table 3. Chemical, physical and biological properties of blister agents
| Properties |
Sulfur Mustard |
Phosgene Oxime |
Lewisite |
| Boiling point(ºC) |
227 |
128 |
190 |
| Vapour pressure at 20 ºC (Pa) |
9,6 |
1500 |
52 |
| Molecular weight |
159 |
114 |
207 |
| Volatility (mg/m3) |
610 at 22ºC |
1800 at 20º C |
4500 at 20º C |
| Appearance |
Pale yellow to dark brown liquid |
Colorless, crystalline solid or liquid |
Pure, colourless, oily liquid |
| Odour |
Garlic or mustard |
Intense, irritating |
Geranium |
| LCt50 (mg·min/m3) |
1500 |
3200 |
1200 |
Blood Agents
A blood agent is absorbed into the body through the lungs where it is then picked up by the blood and carried
to the rest of the body. Blood agents cause convulsions and suffocation, as all blood gases do because they
interfere with the absorption of oxygen by the blood in the lungs.
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