condition may occur on a clear night, a cloudy night, or a cloudy day.
Low wind speeds are also favorable, because this condition keeps the
agent cloud traveling over the area without much diffusion. The most
favorable terrain for a chemical cloud is smooth or gently rolling
contours and wooded areas. Conversely, unfavorable conditions for
chemical clouds (usually found on a clear day) are extreme or marked
turbulence, winds of more than 10 knots, a lapse (unstable air)
condition, rain, and rough terrain.
The most effective weather conditions for a liquid spray attack are a
low wind speed with a small degree of turbulence, high temperature,
high humidity, and the absence of rain heavy enough to wash away the
agent. In wooded areas a high temperature with only a very light wind
will establish the highest vapor concentration. Favorable conditions
above the freezing point of the liquid (this lessens evaporation of
the agent), a low wind speed, wooded areas, and absence of rain.
Unfavorable conditions for liquid agents are high soil temperature,
high wind speed, bare terrain, and heavy rain.
b. Defense Against Chemical Attack.
Mission-Oriented Protective Posture (MOPP) is the principal defense
against chemical attack. MOPP is a flexible system of protection
facilitate mission accomplishment. It requires personnel to wear
individual protective equipment consistent with the chemical threat,
the work rate imposed by the mission, and the temperature. MOPP does
NOT mean that individuals must wear all of their protective equipment
all of the time. In fact, because of duty requirements, body heat
buildup, and basic human needs, personnel cannot wear protective
clothing and equipment for an indefinite period. MOPP does, however,
give the commander and his staff a range of choices of chemical
protection for their units. These choices range from no protection at
all to full-protection clothing and equipment including protective
The five MOPP levels (Table 1-2) are based on the commander's need to
balance protection with the threat, temperature, and urgency of the
mission. The five MOPP levels are:
MOPP Zero -- Overgarment, overboots, and gloves readily
available; mask carried.
MOPP 1 -- Overgarment worn; overboots, mask/hood and gloves