c. Radiological contamination is not affected by weather. Its hazards decay at a particular rate
depending upon the physical characteristics of the particles. This process is called "aging". Aging
requires almost no labor and reduces troop exposure to radiation. Although the radiation decreases with
time, in certain cases, the contamination becomes more firmly fixed to the surface. So, the lack of time
or the nearness of unprotected personnel to the contamination may require the use of a faster method of
decontamination.
d. The effects of weathering or aging include:
(1) Temperature.
High temperature speeds the changing of liquid to vapor (evaporation) and hastens the
dispersion chemical agents in the air. The persistency of liquid chemical agents on the
ground decreases as the temperature increases. Temperature has no effect on radiological
contamination.
(2) Wind.
Aeration aids in decontamination. High winds rapidly disperse chemical agent vapors.
(3) Humidity and rain.
Moisture tends to break down chemical agents. However, most chemical agents break
down very slowly. Heavy rain aids decon by removing contamination; however, runoff
contamination may build up in drainage areas, creating hazards.
Rates at which microorganisms dry out (dehydrate) depend upon the moisture content of
the air. Although some agents (spores) possibly are not affected by low humidity,
periods of dry weather help reduce most biological contamination within an area.
Rain that wets the terrain may prevent the formation of secondary chemical and
biological aerosols. Rainfall may also leach contamination into the soil.
(4) Sunlight.
Sunlight can act as a decontaminant. Even in cold weather, the direct rays of the sun
warm surfaces above the air temperature. This hastens
CM 2506
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