Cold-Weather Operations:
Sustaining Health & Performance in the Cold

TOPICS IN THIS SECTION INCLUDE: How Cold Affects the Body Minimizing Effects of Cold on the Body Insulation, Layering and Ventilation Tent & Shelter Heaters Sleeping Bags Keeping Dry Minimizing Effects of Cold on the Body: Cold-weather clothing systems are designed to change with the wearer's needs. Cold-weather clothing protection is based on the principles of insulation, layering and ventilation. By understanding these principles, Soldiers can vary their clothing to regulate protection and stay comfortable.

WHEN USING COLD-WEATHER CLOTHING,      REMEMBER C-O-L-D: keep it ------- Clean avoid ------- Overheating wear it ------- Loose in layers keep it ------- Dry

Insulation depends on the clothing thickness, properties of the garment material, and the amount of air trapped within the garment. When clothing is dirty, the material tends to be packed down, which compromises insulation. Wearing clothing ensembles in multiple layers allows the wearer to remove or add clothes to adjust the insulation to changes in environment or workload as well as to the individual's own needs and preferences. Wearing layered clothing is especially important for Soldiers whose duties require them to frequently move in and out of heated shelters, or to periodically undertake vigorous physical activity. Physically active people can sweat even in extremely cold weather. Sweat will be able to evaporate if clothing allows ventilation. Proper clothing will be made of material that water vapor can pass through, and will allow the wearer to unzip and open the clothing periodically to increase ventilation. If sweat can not evaporate, it will accumulate, wet the clothing, compromising insulation. Sweat evaporation will be compromised when clothing is dirty. The US Army has two different clothing systems in the inventory for issue to troops operating in cold-weather conditions: a Cold/Wet-Cold/Dry Clothing System (FM 31-70), and an Extended Cold-Weather Clothing System (FM 21-15). Soldiers deployed to cold-weather areas from stations in warm regions are usually issued the combination Cold/Wet-Cold/Dry Clothing System which can be configured into two ensembles. The cold/wet ensemble is worn above 14°F, and the cold/dry ensemble is worn below 14°F. The cold/dry ensemble protects down to -60°F. The cold/wet configuration differs from the cold/dry in the number of layers and the choice of boots. The system uses layers of wool/cotton fabrics to trap air for insulation, and a water-repellent outer garment to maintain dryness. Soldiers regularly stationed in cold-weather regions are usually issued the Extended Cold-Weather Clothing System (ECWCS) which protects from +40°F to -60°F. ECWCS consists of 5 layers: polypropylene underwear, a polyester fiberpile shirt and bib overalls, polyester coat liner and nylon/cotton field pants, nylon/GORE-TEX ® laminate parka and trousers, and white nylon/cotton overgarments (parka and trousers). The inner layers are made of fabrics which draw perspiration away from the skin. The outer layer is made of a material which repels outside water while allowing perspiration to be evaporated. Either the cold-weather vapor barrier boot (Type I) or the extreme cold-weather vapor barrier boot (Type II) can be worn with one pair of nylon/cotton/wool socks (OG-106). The Combat Vehicle Crewman's Hood (Balaclava) is worn under the PASGT helmet. The polypropylene layer and the nylon/GORE-TEX ® Parka and trousers should always be worn to prevent perspiration from building up inside the clothes. Wool or wool blends should not be worn in the intermediate layers of the ECWCS because they retain moisture. Several varieties of handwear protection are available for issue. Most Soldiers receive the standard light-duty leather glove which is worn with a 50% wool, 50% nylon liner inserted. This handwear ensemble provides inactive persons with about 30 minutes of protection from frostbite when air temperature is 0°F. If temperatures are warmer and/or Soldiers are physically active, the handwear ensemble will provide effective protection for longer periods. The light-duty leather glove is not waterproof. When the standard light-duty leather glove provides inadequate protection, (i.e. air temperature below 0°F, or more than 30 minutes of inactive exposure anticipated) trigger finger or Extreme Cold Weather mittens and liners can be worn. Because cold-weather clothing is heavy and cumbersome, it greatly increases the energy required for physical activity. The increased effort can result in overheating and sweating especially during hard work, and can contribute to increased fatigue. Perspiration buildup should be minimized by opening clothing and removing layers during heavy work and scheduling frequent short rest breaks. Wind-chill temperatures are widely reported by television and radio meteorologists, but they really only estimate the danger of cooling the exposed flesh of inactive persons. Windproof clothing greatly reduces windchill effects. Rather than cancel outdoor training at some arbitrary temperature limit, training should be modified and safety surveillance should be increased as the weather becomes more severe, and the danger of tissue freezing increases, as indicated in Appendix B. The US Army has several heaters for use inside tents during cold weather. The type of heater required depends on the size of the tent or shelter to be heated. Usually, the Yukon stove is used to heat the Arctic 10 Man Squad Tent, 5 man tents and GP small tents. The Squad stove M1950 is used in improvised shelters or small tents housing 2 to 5 men. Larger capacity stoves are available for the bigger tents. All these stoves provide heat and can be used to melt ice and snow or to heat water. Care must be used to prevent melting the frozen ground beneath or around the stove. By using a tent liner, removing loose snow and ice from the ground before setting up the tent, and preventing the tent from overheating melting can be minimized. If available, plywood tent flooring and metal trays under the stove can be used to reduce melting. Shelter from weather is critical. The standard shelter is the tent, but improvised shelters (snow caves, snow trenches, lean-tos etc.) can be constructed from local materials. The recommended sleeping system is the Extreme Cold-Weather Sleeping Bag (NSN 8465-01-033-8057), on top of a polyfoam sleeping mat (NSN 8465-01-109-3367). Layers of tree boughs or mats under the sleeping bag help prevent heat loss to the ground. The sleeping bag should be shaken out before using to add air to the lining, which improves its insulation. In tents, Soldiers should sleep in long underwear and socks with all other clothing hung up to dry. In improvised shelters, only boots and the outermost clothing layer should be removed. Place clothing under the sleeping bag where it can add insulation without accumulation moisture from the body. Ice should be removed from vapor barrier boots, and they should be wiped dry on the inside and, if possible allowed to air out before putting them on again. In extreme cold, a balaclava or some other head cover should be worn while sleeping to protect the ears, neck and face. The arctic mittens can be worn on the feet while inside the sleeping bag to help keep the feet warm. The head should not be put inside the sleeping bag, since moisture from the breath will accumulate in the bag. Air out the sleeping bag as often as possible to evaporate moisture. Feet, hands and exposed skin must be kept dry. Feet are particularly vulnerable and extra foot care is required for cold-weather operations. Feet should be washed, dried and dusted with a dry, antifungal powder (NSN 6505-01-008-3054) daily. Socks must be changed whenever they become wet from exposure to rain or snow, or from excess sweat. This may require changing into dry socks at least 2-3 times daily. Extra socks can be air dried and then carried under BDU's to warm. Humans protect themselves from cold primarily by avoiding or reducing cold exposure using clothing and shelter. When this protection proves inadequate, the body has biological defense mechanisms to help maintain correct body temperature. The body's internal mechanisms to defend its temperature during cold exposure include vasoconstriction and shivering. When these responses are triggered, it is a signal that clothing and shelter are inadequate. Vasoconstriction is the tightening of blood vessels in the skin when it is exposed to cold. The reduced skin blood flow conserves body heat, but, as described earlier, can lead to discomfort, numbness, loss of dexterity in hands and fingers, and eventually cold injuries. Cold triggers shivering. Shivering increases internal heat production which helps to offset the heat being lost. Internal heat production is also increased by physical activity, and the more vigorous the activity, the greater the heat production. In fact, heat production during intense exercise or strenuous work is usually sufficient to completely compensate for heat loss, even when it is extremely cold. However, high intensity exercise and hard physical work are fatiguing, can cause sweating and cannot be sustained indefinitely. Moreover, most military occupational activities are less vigorous than high-intensity exercise, so internal heat production will probably not be adequate to offset heat loss. Susceptibility to cold injuries can be minimized by maintaining proper hydration and nutrition, avoiding alcohol, caffeine and nicotine, minimizing periods of inactivity in cold conditions. Minimize the risk of cold injuries in fighting positions, sentry points and observation points by placing pads, sleeping bags, tree boughs, etc inside these positions to allow occupants to insulate themselves from the ground or snow. High levels of physical fitness are also beneficial for Soldiers participating in cold-weather operations. Humans do not acclimatize to cold weather nearly as well as they can acclimatize to hot weather, although repeated cold exposure does produce what is referred to as habituation. Proper training before deploying into cold-weather regions is more important for prevention of cold injuries than repeatedly being exposed to cold temperatures. Following habituation, shivering is much less vigorous. This is advantageous because shivering is inefficient, and most of the heat produced is lost. Also, shivering can interfere with sleep causing fatigue. With habituation to repeated cold exposure, humans adjust mentally and emotionally. Training outdoors in cold weather before deployment will help build confidence in Soldiers' ability to physically, mentally and emotionally contend with the stress of cold-weather conditions.

Source: SUSTAINING HEALTH & PERFORMANCE IN COLD WEATHER OPERATIONS