|
Heat
loss occurs through conduction, convection,
evaporation, radiation, and respiration. Heat
loss through conduction and convection can be
minimized through the use of insulation and
wind-proof materials. Clothing should be worn
in layers to trap several layers of still air
warmed by body heat.
The best
fabrics are wool and polypropylene, with polyester,
acrylic, and similar synthetics a close
second. Cotton has poor insulating value,
especially when wet. These fabrics are worn
typically as the innermost two or three
layers. Outer layers should be of
"lofting materials" such as polyester
and nylon pile and fleece. The outermost layer
should be windproof and of a water resistance
fabric. Heat
loss by evaporation is avoided by
wearing water-repellent outer garments, by
drying off quickly or changing into dry
clothes when wet, and by removing layers when
too warm to avoid perspiring. Heat
loss by radiation is avoided principally
by wearing a hat. Circulation to the head is
not reduced in the cold, and up to 70% of
total body heat can be lost through an
uncovered head. Body
parts with a large surface area to volume
ratio (nose, ears, toes, and fingers) should
be protected. Mittens are preferable to
gloves. Tight boots and other garments, which restrict
circulation, should be avoided. In cold windy
weather, a facemask should be worn, and in
extreme conditions the individual should seek
shelter. Alcohol and tobacco should be avoided
during cold exposure. |