Dehydration (leading to heat stroke) and hypothermia are two of the biggest killers in the wilderness. You need to guard against both these situations. Our normal core body temperature is 98.6°F. A few degrees over or below this average and you could be looking at serious trouble.
Once you are struck with heat stroke or hypothermia, the body’s cooling mechanism shuts down and death can come very quickly.
The trick is to be help the body control its core temperature and not let it get out of sync. First, we need to know the ways by which we can gain or lose body heat. There are six ways. When you are constructing shelter, you need to be aware of each of these ways through which you could send your body temperature out of whack. And don’t think that a fancy sleeping bag is going to protect you. It will protect you for some time, but ultimately, one of these six ways will sneak in and make life miserable.
The six ways body heat is gained or lost are conduction, convection, radiation, respiration, perspiration and immersion. Let us look at each of them to know what they are.
Conduction: This is how thermal energy (or heat) transfers from one source to another through direct contact between the two bodies, to try and bring about an equilibrium in temperatures between them. For instance, if you sit on a block of ice, the higher body heat transfers on to the cooler ice slab. This results in losing body heat through conduction. Conversely, if you sit on the hot desert sand in the mid day Sun, the cooler body gains heat from the hotter sand, resulting in raising body heat through conduction.
Convection: Convection is a way of losing body heat due to the movement of wind. When there is a wind blowing it reacts with the surface of the skin. When the wind is cold (like in the mountains) it pulls heat from your body and when the wind is hot (like in the desert) the skin pulls in heat from the wind. And this is not just for hikers and trekkers or those on foot. If you are on a motorcycle, even if the wind is still, the speed of your motorcycle determines wind speed. And this affects how your body loses or gains heat.
Radiation: Radiation is essentially heat gain or loss from or to space. You would have noticed this quite often. Standing under a tree in the heat, makes life more comfortable. Standing under a portico on cold night is somehow warmer. Our warm body radiates heat out into space and the portico is trapping it providing a sensation of relative comfort. When the Sun is not shining, at night, the only thing that will be warm around you is your body. And it will radiate heat out of the body. To prevent heat loss through radiation, you need to trap as much heat that is radiating out of your body. That is where a roof over your head, in your shelter, becomes imperative.
Respiration: We may not realise this, but we lose body heat through the sheer act of breathing. Every time we breathe in cool air, we breathe out warm air, and a little bit of body heat escapes. Ever seen yourself cupping your palms together in the cold and breathing into it? You are breathing warm air onto your palms, warm air escaping through breathing. And not only heat, moisture escapes from your body every time you breathe. Do not work too hard because if you do you will lose a lot of body heat, because you will be breathing harder. Also, try not to breathe through your mouth, more heat escapes from the mouth than it does through the nostrils.
When you are building shelter, you need to make it warm enough so that the air you are breathing in is almost as warm as the air you are breathing out. If that is difficult, put a scarf or a muffler over your face. Every time you breathe out, it will warm the fabric and every time you breathe in, the air will heat up just a little bit due to the warm fabric.
It is possible to breathe in air so cold that your lungs get frostbitten.
Perspiration: When we are hot, we sweat. Sweat is the body’s way of keeping cool. It is also a way of the body losing excess heat. Every time we sweat we cool the body. In extreme cases of dehydration, heat exhaustion and heat stroke, you can actually stop sweating. So your shelter needs to be cozy enough not to allow you to sweat.
Secondly do not panic. When you panic, you start to become over anxious leading to hyper activity. This results in no solution from your predicament, but leads to heat and fluid loss through perspiration.
In particularly cold weather, when you are doing a lot of exercise (mountaineering being a case in point), you will tend to sweat. The sweat will form icicles, leading to frost bite.
So, all in all, sweating is not such a good idea. Reduce it to prevent heat loss and fluid loss.
Immersion: Wetness is almost a sure way of getting hypothermia. And immersion could be through sweat, rain, snow, and of course, immersion in water. The combination of wetness, cold weather and wind is a sure shot formula for hypothermia. You need to reduce all three conditions if you want to stay healthy. If you are wet, get dry. Being naked in the snow or rain is better than wearing wet clothes in the snow or rain. If you want to stay alive, stay dry. Your shelter has to be waterproof.
Once you are aware of these six ways your life could be put in jeopardy by Mother Nature, you can take preventive actions. Never allow core body temperature to go to extremes. The range is pretty narrow. A few degrees below or above normal core body temperature and you could be in serious trouble. Act decisively, consciously and with purpose to prevent a problem. It is always a better idea to be preventive rather than reactive.