The air is crisp, crystalizing around you with each breath. A twig snaps under the pressure of your foot, echoing off the surrounding trees. It’s a brisk, beautiful late autumn morning. It’s great to be in God’s creation.
But for the ill-equipped traveler thrust into survival mode due to mechanical issues with his vehicle, the same picturesque morning can be cold, hard, unforgiving, and even life-threatening.
The right gear makes a world of difference. So what’s the right gear? In previous article, I’ve written about the best way to dress for cold weather. In this post, I’ll share the 5 ways your body looses heat. Understanding these methods can help you to reduce your heat loss and stay warm longer.
Heat Loss Through Radiation
As warm blooded beings, people produce their own heat. By just being alive, we create a normal body temperature of 98.6F. Most the time that’s warmer than our surrounding environment, so the two try to equalize. Our body gives off heat through radiation. That’s when the warmer of the two areas gives off heat to the cooler area.
To control heat loss through radiation, we need to insulate the ourselves from the surrounding environment. We can do this through warm clothing.
A down jacket, for instance, uses our body heat to warm the pockets of air trapped in the down. That helps keep the heat inside the jacket and thus keep us warm.
Your head is a major source of heat loss. Keeping your head covered, and the area around your neck can help preserve your heat.
Heat Loss Through Conduction
Another way our bodies loose heat is by coming into direct contact with another surface that is at a lower temperature. It’s similar to radiation except rather than loosing heat to the environment, the heat is transferred to another object or surface.
Solid objects such as a metal pole or the ground can steal heat from your body much more effectively than air. In fact, you loose heat about 30 times faster when submerged in water than standing in air. 75F in air feels comfortable; 75F in water is feels cold and can cause hypothermia.
Conduction is why it’s important to insulate yourself from the ground when sleeping. Body heat will seep into the cold ground, leaving you cold and miserable. Sleeping on evergreen boughs will help lift you off the ground and preserve your body temperature.
Heat Loss Through Convection
As with radiation, convection is when your body looses heat to the surrounding environment. However, with convection, the heat loss is through the stirring of the air.
Consider a fan. When you are sitting in your home and you’re a little warm, you may turn on a fan to help circulate the air. The moving air brushes by your skin. When it does, it takes a little bit of your heat with it. Then, having moved along, more air brushes by, taking more of your heat. The more air, or wind, the more heat loss.
This is sometimes called “wind chill” and it can be devastating for the survivor in colder climates.
When dressing during cold weather, it’s important to keep in mind that your outer layer of clothing should protect you from the wind.
Heat Loss Through Evaporation
Our bodies have a built in system to help regulate excess heat. When we exert ourselves and our core body temperature rises, we begin to sweat. On a hot summer day, sweating is a good thing. In fact when you stop sweating, you should be worried about overheating.
However in the winter, sweating is bad. In fact it can be deadly. As renowned survivalist Les Stroud has said, “In cold weather if you sweat, you die.” But the threat is not limited to sweating. In cold weather survival situations, you must stay dry. Rain, mist, snow, and other forms of liquid will have the same effect is sweating.
When water, including sweat, evaporates it cools the adjacent surface. When that surface is your skin, it removes much needed heat from your body and makes it harder to stay warm.
In cold weather, you must stay dry. Having the proper clothing is important. Avoid overexertion. Regulate your body temperature to avoid sweating by removing layers of clothing when you do strenuous activities. Stay dry.
Heat Loss Through Respiration
When you breathe, you were bringing in cold air from the outside into your lungs. As oxygen is transferred to your bloodstream and carbon dioxide is transferred out, your body warms the air. When you exhale, you’re releasing the warmed air into the surrounding environment. That is heat loss through respiration.
Compared to the first four sources, heat loss through respiration is relatively minor. But still you should be aware of it. A light covering over your face will help pre-warm some of the air before bringing it into your lungs.
As fall is giving way to winter, it’s important to understand how our bodies can lose heat and how to avoid it. Hopefully if you’re thrust into a survival situation, you’ll have the proper clothing and gear. But being prepared is as much about knowledge and skills as it is about gear.