Layering

Clothing maintains the body's microenvironment best when it is worn in multiple layers, letting you adapt easily to the fluctuating temperatures in the mountains. To keep pace with changing conditions, add or subtract layers of clothing one by one.

Three levels form the basis of this clothing system: a layer next to the skin, insulating layers, and an outer protective layer.

The layer next to the skin (long underwear) allows for ventilation so the body can cool itself. During the warmer parts of a day, many climbers wear just their long underwear and a pair of shorts. When it's cold, long underwear, covered by additional clothing, increases your insulation. This layer also transports perspiration away from your skin without absorbing the moisture. (Wet garments in contact with your skin draw away twenty-five times more heat than dry ones.)

The insulating layers (shirts, sweaters, pile coats) trap warm air next to the body. The thicker the layer of trapped or "dead" air, the warmer you'll be. However, several light, loosely fitting layers are usually warmer than one thick garment. They are also more versatile because the various pieces can be worn in different combinations depending on the temperature and your level of exertion.

The outer protective layer is essential for minimizing heat loss from wind and rain. Wind stirs up the warm air next to the body and blows it away, a process known as convection. The stronger the wind, the faster heat is blown away, producing a wind-chill effect that makes it feel much colder. When the air temperature is 10 degrees Fahrenheit, a 20-mile-per-hour wind produces a wind-chill effect (fig. 2-7) that is equivalent to -25 degrees. Rain dampens clothing and reduces its insulating

Fig. 2-7. Wind-chill chart

Wind Speed MPH

Temperature (°F)

Equivalent Chill Temperature

Calm 5 10 15 20 25 30 35 40 above 40

' ¿ssÄ^ör""'1 •-■•■"•■■•■■"■■

little additional effect

Great

Extreme

Danger of Freezing Exposed Flesh if Dry and Properly Clothed:

Little Danger

Great

Extreme

To use this table, which illustrates the intensely chilling effect of wind, find wind speed (in miles per hour) in left-hand column and temperature (in degrees F) in top row; the intersection of these is the equivalent temperature. For example, at a temperature of 0°F a breeze 15 mph has the cooling effect of a temperature of -36° on a calm day and precautions should be taken to protect exposed flesh from frostbite. The zones shown on the table indicate the danger of frostbite to any exposed flesh of an average person in good condition whose body is properly clothed for the conditions. When the effective temperature is -25°F or less, care should be taken to minimize exposure of bare skin to wind.

value, and wet clothing conducts heat from the body at an alarming rate. A waterproof shell over your insulating layers eliminates heat loss from conduction and convection. Wind cannot penetrate the shell, so warm air next to your body stays put. The shell also keeps the insulating layers drier so that body heat is not conducted away.

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