There are two kinds of cold to be concerned about: dry and wet. Dry cold is the result of wind, temperature, and the combination of the two known as wind-chill factor. Approximately 60 percent of a person’s energy is used to keep the body warm, so when exposed to cold, the body’s temperature decreases. This in turn causes blood vessels to constrict, slowing blood flow to the skin. For these reasons, exposed skin can lead to frostbite and hypothermia. Wet cold involves direct contact with water, immersion in water, or contact with dampness in the air, like sleet or freezing rain. The body tends to lose even more heat when exposed to wet cold. A body in wet clothing can lose heat up to 24 times faster than it would in dry clothing. Keeping clothing dry in cold, wet environments can be a challenge. The most common and serious problems associated with the cold are frostbite, trench foot and hypothermia. The severity of cold hazard depends on the air temperature, moisture and wind; length of exposure time, and dress and health of the exposed person. The temperature does NOT have to be below freezing for people to suffer cold injuries.
Frostbite occurs when parts of the body literally freeze; it causes tissue damage and often starts where the body is most exposed—areas like the nose, hands and feet. Physical signals of frostbite include numbness and lack of sensation (pain may occur initially and later subside). The skin may appear waxy or discolored. Since frostbite occurs in stages, skin can appear flushed, white, yellow or blue depending on the degree of frostbite. Blisters may form, but they should NOT be broken. Gangrene and amputation are severe consequences of frostbite.
Hypothermia is when the body loses more heat than it can replace; the body cools to an unsafe internal temperature. A person experiencing hypothermia may shiver, feel numb, have a glassy stare, not care about anything, and lose consciousness. They may be confused, irritable, clumsy, irrational and bluish in color. Hypothermia is a medical emergency and death will occur if it is allowed to progress. Victims also can suffer frostbite.
Precautions: The best precaution for frostbite and hypothermia is exposure prevention. It is best to dress the torso area in layers. The outer layer should protect against the wind and allow ventilation, and may prevent water penetration. Garments that breathe but do not allow water to penetrate are good choices. For an insulating middle layer, consider the benefits of wool or synthetic fiber. Down is a good insulator, but it becomes ineffective when wet. Thermal underwear is a common inner layer. Good ventilation is key to keeping the skin as dry as possible.
Protecting extremities requires coverings for feet, head and hands. Footwear should be insulated to protect against cold and dampness. Because of the large amount of blood that circulates to the brain, up to 40 percent of body heat is lost when the head is exposed. Jackets with a hood attached, or other head covering that is intended for cold weather, will substantially cut loss of body heat. In addition to the weather, the work that hands need to do will determine glove type. When the weather is cold and wet, waterproof insulated gloves provide the best protection. Glove liners will provide extra insulation for the hands.
Cold-related emergencies can be prevented by adequate planning: