Heat, a rather mundane topic. If you are cold, add heat, if you are hot, offload heat (adding cold can get complicated, bear with me. Our bodies are fragile, at all ages, when it comes to temperature. A few too many degrees up and heat exhaustion can cause death, a few too many down, hypothermia can produce the same result. Hypothermia can occur when your core temperature drops below 95 degrees, just 3.6 degrees from “normal” – yikes, my cocktail loses that many degrees in the short walk from my back door to the pool. Yikes! Fever, the same in the opposite direction – a little too much tobacco in my Bloody Mary and I feel “the fever”!
Writing this, in Phoenix, with the outside temperatures currently hoovering north of 118 degrees, for the third day in a row, makes “heat” the elephant in the room. Knowing I could have left a frozen turkey on the passenger seat of my vehicle when I got here this morning, that I could safely eat on my drive home makes one think of these things.
Heat is something we need to plan to manage to survival. There are three things we need to do with heat – generate it, dissipate it or preserve it, no matter where we find ourselves. Planning for the generation and/or offloading of heat will go a long way in keeping us alive and as comfortable as can be expected when we need to execute our survival plans. We will focus on heat loss in this article. Heat is lost in four ways – convection, radiation, conduction, evaporation.
This subject can get very complex very fast, so I am going to try and just address some of the basics here, and build on the tangents in a later posting.
I am going to assume you know all about fires, how to make them (without having to rub two sticks together), maintain them, control them, extinguish them, and you have a basic understanding of how to find shade, water, and all the other things that will cool you, as much as possible. If not look in our archives.
Let’s walk through this – convection is when you lose heat through contact. The ground, the air around you, wind. Radiation is when you lose heat through your skin and clothing. It is closely tied to convection as we radiate heat (generate heat higher than the temperature around us) and the body naturally does this to maintain “normal.” Conduction is when we transfer heat by contact with physical objects, like snow, or again the ground. Again, the difference between this and convection is subtle. Then we have the easy one, evaporation, where we cool by excreting moisture (swear) that evaporates depending on the dew-point, which is a factor of air temperature, movement and moisture content. As anyone who has been to Florida in July can tell you, evaporation doesn’t work there. Heat is a very complex science, taught at the graduate level in college Physics. The simplest answer is heated molecules move faster that cooled ones and the transfer of energy when the two come in contact causes heat loss (they slow down). While it is molecular physics, we feel each of these so we understand them at a sufficient level.
So, what’s our move to manage this? Two very basic thing that can’t be repeated too often. Clothing/cover and hydration. While there is nothing like a raging camp fire (smoke, light that can be seen for 10 miles, s’more if you are lucky), having a shelter and a dry layer between us and the ground is just as important. Clothing that breathes you already know, as well as layering. Dressing for the conditions. How many times have you been hiking and seen people wearing the wrong clothing, shorts and a tank top, when the temperature is dropping. My favorite, a hoodie and shorts during a snow storm. This is only eclipsed by statements like “I am from Minnesota and this is like summer to us”. Good, but you are losing heat and burning stored calories to do so. If it is a trip to the store to get more cough syrup (Monster, Rockstar, 5-hour caffeine jolt, etc.) fine. And please don’t get me started on flip flops unless we are chilling at a warm beach. When we plan, we should consider all the things we can do to “manage heat”. To again, generate it, dissipate it or to store it.
And this includes hydration as the body regulates its internal temperature through a complex process called thermoregulation. The more hydrated a body, the less effort to move blood through the artery system to manage perspiration rates, higher when hot, reduced when cold, which in turn lowers heart rates, which in turn conserves energy, which in turn conserves calories. All things interconnected.
Source: Prepper Articles