Emergency Warmth

Our bodies lose heat in the following ways:

Conduction

Conduction is the transfer of heat from a warm object to a cold one when the two objects are in contact with each other. Conductive heat is easy to experience when you hold a very cold object and feel the heat loss in your hand. The best way to prevent conductive heat loss in your hands is to use gloves or mittens and warm packs.


To prevent heat loss from your body, use a closed cell foam pad or a cushion when sleeping or sitting on the ground or a cold surface. These pads are excellent insulators for the space they use.

Heat can be lost through your feet when the ground is cold and you do not have proper insulation. It is best to have winter shoes (with solid soles, insoles of closed cell or felt material) and synthetic or wool socks. These provide an excellent barrier to prevent heat loss through conduction.

Convection

Convection is heat being carried away by a liquid or a gas (especially the wind). Convective heat loss occurs when warm air next to the body is replaced by cool air from the outside. The best way to minimize convective heat loss is to wear windproof outer clothing.

Evaporation

Evaporation occurs when a liquid changes to a vapor. In the summer, people experience this when they sweat. The body produces sweat (water) on the skin’s surface. The water then evaporates, taking heat from the skin.

When someone is active in cold conditions, sweat is formed on the skin’s surface in response to excess heat caused by over dressing or a high activity level. Later, the person becomes less active (while resting or sleeping), any remaining sweat will still be evaporating, causing unwanted heat loss. To prevent this, a person can take off outer clothing when they begin to become overheated or decrease their activity level in order to minimize sweating.


Respiration

Respiration combines the processes of evaporation (of moisture in the lungs) and convection (displacement of warm air in the lungs by cold air from the cold winter environment).

Significant moisture (and thus, body heat) can be lost when that moist air is exchanged with much drier outside air. In addition, some body heat is lost by warming the cold air entering your lungs.

Respiratory heat loss can be significant in cold, dry conditions. It can be minimized by breathing air that has been pre-warmed and/or pre-humidified prior to taking it into the lungs. Breathing through a fleece headgear increases the humidity and warmth of the air being breathed, prior to its entry to the lungs.

Radiation

Radiation is the transfer of heat energy through empty space. The best defense and a great method to minimize the loss of heat through radiation is to wear a reflective barrier, such as an emergency blanket or bag. This material reflects up to 80 percent of radiant body heat.

The second defense to prevent heat loss due to radiation is to wear thick clothing (down or high-loft synthetic fill garments). Infrared radiation cannot travel through thick insulation, and thus, most of the infrared radiation lost by the body can remain trapped in the clothing rather than exiting out to the environment.

Conclusion

When preparing for the future, remember that emergencies can and often occur in the winter time. Prepare by having warm layers of clothing, a poncho, tent or shelter of some sort, good winter shoes, sleeping bags made of synthetic materials and include a closed cell foam pad. Have methods to produce heat like warm packs and fire making equipment. Use your equipment and become educated to prevent suffering.