d. Clothing. In warfare, where exposure to cold may be prolonged, adequate
and properly worn clothing is essential to welfare and survival.
Clothing for cold weather combat has been designed to be worn as an
assembly for protection of the head, torso, and extremities.
Failure to wear the total assembly and inadequate supplies of proper
sizes of clothing are important factors in cold injury.
The assembly depends upon the layering principal to conserve body
--Loose layers of clothing with air space between them and worn under
an outer wind and water-resistant garment provide maximum protection.
--Some of the layers may be removed during strenuous physical exertion,
for comfort, and minimize perspiration in higher ambient temperatures.
Clothing made wet by perspiration loses much of its insulating value;
therefore, care must be taken to prevent perspiration from accumulating in clothing.
In all forms of cold injury, conservation of body heat is important. All
articles of clothing should be worn loosely, without constriction or tightness.
Clothing should be kept free of grease and dirt since grease and dirt
promote heat loss.
e. Duration of Exposure.
(1) Immersion syndrome /trench foot. The duration of exposure needed to
cause immersion syndrome varies according to the ambient (air) temperature and the
temperature of the water. The average duration of exposure resulting in trench foot is
three days at a temperature range of 32 to 50 F. The time needed to cause trench
foot usually ranges from a few hours to 14 days.
(2) Frostbite. The average duration of exposure resulting in frostbite is 10
hours, with a usual range of 1 to 20 hours. The time varies for different types of activity.
A decrease in physical activity reduces the exposure time necessary to produce cold
injury. For patrols and other offensive maneuvers, for example, the period of greatest
susceptibility usually begins at that time when walking ceases either because of arrival
at an ambush site or because of being pinned down by the enemy.