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Survival Shelter and Protection from the Elements
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Stay Alive: Survival Shelter and
Protection from the Elements
Learn about your body’s thermoregulation, what protection it needs
and how to build a storm shelter for protection.
By John D. McCann
There has been rigorous debate about whether fire or shelter is the first
priority for survival. I see them as equal in importance, and as two options
where, ultimately, one is chosen depending on circumstances. If you are in a
warm climate and it looks like rain, a shelter would be an appropriate course of
action. However, if you are in the northeast in the winter and it is below zero,
you need a fire, especially if you fall through the ice and get wet. You have a
very short time to get warm and dry, or you’re going to die. Once you are warm,
you’ll be able to build a shelter for protection from the elements. Again, the
situation will dictate which of the two is the priority.
Since we covered fire in the previous chapter, let’s now examine the ways
Since we covered fire in the previous chapter, let’s now examine the ways
your body heat can be transferred to the environment, and how a shelter protects
you from the elements and helps prevent that loss.
Heat loss mechanisms
The ways that heat from your body can be transferred to the environment are
called heat loss mechanisms. In a cold environment they can all be detrimental,
but in a hot climate some of these mechanisms can be used to your advantage.
Radiation
Radiation is the primary cause of heat loss. Our body radiates heat to the
environment much like the sun radiates heat to the earth or a campfire radiates
heat to keep us warm. At 50 degrees F, 50 percent of the body’s heat can be
transferred to the environment through an exposed head and neck. We can also
lose heat from our wrists, hands and feet. Have you ever had your mother or
father tell you if you want warm feet to cover your head? Wearing a hat, scarf,
wrist-overs or gloves can help eliminate loss of heat through radiation from your
head, neck and wrists. A shelter can help reduce loss of body heat to the
environment by holding it inside the shelter.
Conduction
Conduction is the process by which we lose heat through direct contact
between objects. This can occur when sitting on a cold or snow-covered stump
or rock, when wet clothes come in contact with your body, by touching cold
objects with bare hands, or by kneeling on the snow to build a shelter. Avoid
these situations to prevent conduction of heat from the body to other objects.
This is another reason to insulate between yourself and the ground in a shelter.
In the winter, I carry a small closed cell foam pad, cut from an old military
sleeping pad, in the back of my pack. I use it to insulate myself from a cold
object when sitting down.
Convection
Convection is loss of body heat due to movement of air or liquid across your
skin. An example of convection is wind chill. Through radiation, the human
body is always warming a thin layer of air next to the skin. The temperature of
that layer of air is usually equal to that of the skin. When this layer of warm air
is undisturbed, the body stays warm. However, if this warm layer is removed by
convection, the body quickly cools down. In cooler environments, clothing is
your first line of defense, as it helps hold that thin layer of warm air near your
skin.
Evaporation
Evaporation is a process whereby liquid changes to vapor, during which heat
from the liquid escapes to the environment. In a cold environment, it is essential
to wear fabrics that breathe. If water vapor from perspiration cannot evaporate
through clothing, it will condense, freeze and reduce the insulation value of the
clothing. This will cause your body temperature to go down. However, in a
warm environment evaporation can be used to your advantage. Have you ever,
warm environment evaporation can be used to your advantage. Have you ever,
on a hot day, worn a wet T-shirt or a wet bandana around your neck? This is also
evaporation at work, because as the water is evaporated it pulls heat from the
body, cooling you. It is called evaporative cooling. At our camp, we use this
method in the summer by placing wet towels on water containers to keep the
water cool.
Respiration
We lose heat through our normal breathing process. You can observe this
when you see a person’s breath on a cold day. This is heat from the body lost to
the environment. It is also difficult to prevent this loss, as we have to breathe.
Heat regulation in the human body
Hypothermia
Often called “the killer of the unprepared,” hypothermia is a real threat to
survival. The three main elements leading to hypothermia are cold, wind and
wetness. Keep in mind it isn’t necessary for temperatures to be at or below
freezing for hypothermia to occur. Many instances of hypothermic death have
taken place in temperatures over 50 degrees F. Hypothermia is heat loss at the
body core, and it results from exposure to cold with the addition of other heat-
loss mechanisms or nature’s elements.
Normal body temperature is 98.6 degrees F. If core body temperature drops
below 95 degrees F, your body will not generate enough heat to maintain normal
body functions and hypothermia sets in. If your body temperature drops below
92 degrees F, you won’t be able to help yourself survive!
In the case of mild hypothermia (between 91 and 95 degrees F), normal
shivering begins and ranges from mild to severe. You might have a cold
sensation and have goose bumps, your hands can be numb and you might not be
able to perform complex tasks with your hands.
In moderate hypothermia (between 82 and 90 degrees F), shivering becomes
intense. There is an obvious lack of muscle coordination and movements become
slow and labored. Violent shivering continues, and speech, thinking and gross
slow and labored. Violent shivering continues, and speech, thinking and gross
muscle movements become difficult. The use of hands often ceases and
stumbling becomes frequent. This is a serious situation.
In severe hypothermia, below 82 degrees F, you are in major trouble. All
shivering stops and exposed skin becomes blue or puffy. You are confused,
unable to walk and muscles become stiff. You lose awareness of others, if
present, and the pulse and respiration are erratic. At this point, unconsciousness
occurs and death usually follows.
A good survival kit should contain the items you need to avoid falling prey to
hypothermia. You need to be prepared in order to protect yourself from the cold
and effects of hypothermia.
Hyperthermia
Hyperthermia is elevated body temperature which occurs when the body fails
at thermoregulation; and the temperature control system becomes overloaded.
The body is normally able to cool itself through sweating, but under some
conditions sweating is not enough and body temperature can rise rapidly. If the
temperature continues to rise, it can damage the brain and other vital organs and
result in death.
There are three levels of heat related injuries: heat cramps, heat exhaustion
and heat stroke. Heat injuries are a serious matter.
As indicated earlier, normal body temperature is 98.6 degrees F. When your
temperature is between 99 and 100 degrees F, you are at risk of heat cramps, the
least serious heat injury. Heat cramps normally result from over-activity in a hot
environment and are connected to dehydration and poor conditioning. Initially,
you’ll begin to feel cramps in the abdomen and legs. You’ll have hot sweaty
skin, may feel nauseous or dizzy, and may have a headache. When this happens,
rest, drink water and, if possible, move to a shady, cool environment.
Evaporative cooling, discussed above, and staying hydrated can help prevent this
stage.
In the next stage, heat exhaustion, the body temperature rises to 101 to 102
degrees F. Symptoms can include extreme thirst, headache, nausea, rapid pulse
degrees F. Symptoms can include extreme thirst, headache, nausea, rapid pulse
and breathing, and exhaustion. These symptoms also describe the early stages of
shock. Persons at this stage may often feel cool because of profuse sweating.
The last stage, and most severe, is heat stroke. This occurs when the core
temperature is between 103 and 106 degrees F. Victims of heat stroke may have
a sudden change of behavior, become disoriented, hallucinate, become irritable
or speak incoherently. A heat stroke victim will have elevated and rapid
breathing. Seizures are common in heat stroke victims and, if left untreated,
death follows.
As you can see, heat injuries can be dangerous and even fatal. We will discuss
treatment for both hypothermia and hyperthermia in Chapter 11, Wilderness
Hazards & Safety.
Clothing as a defense against hypothermia and hyperthermia
The clothing you have on your back or with you when a survival situation
occurs is always your first line of defense as shelter from the elements.
Understanding the advantages of various types of clothing, and the proper
layering of that clothing, helps you to protect yourself from the heat loss
mechanisms.
First, let’s address a cold environment. One of the keys to preventing
hypothermia in cold weather is to dress properly. The best way to dress for the
cold is by layering. There are three basic stages to proper layering, the base
layer, the insulation layer and the protective shell layer.
Base layer
The base layer is the clothing next to your skin. This layer should be material
that will wick moisture away from your skin, and could be synthetic, such as
polypropylene, or made from natural fibers, such as merino wool or silk. Merino
wool is an exceptionally good choice since it absorbs moisture while still feeling
warm and dry to the touch. It also does not absorb skin oils, which helps to avoid
that “been-living-in-these-awhile” smell.
Avoid cotton in the winter for any layer, and definitely never use it as a base
Avoid cotton in the winter for any layer, and definitely never use it as a base
layer. Cotton absorbs water like a sponge, takes a long time to dry and, when
wet, feels damp and clammy. No matter what you layer over it, you will quickly
feel chilled.
The base layer should fit snugly without binding or chafing and allow for
freedom of movement.
Insulation layer
The second layer is the insulation layer. This layer should also be breathable
and trap a layer of warm air next to the body, keeping body heat in and cold out.
This layer would include your shirt, pants, sweaters (wool preferred), and a wool
or fleece jacket. This layer must maintain its ability to insulate even when wet,
and then dry quickly.
Protective shell layer
The third layer is the outside protective shell layer. This layer protects you
from the wind, rain or snow, and should be wind and waterproof while also
ventilated to allow moisture to evaporate or escape. Some fabrics to consider are
Gore-Tex or laminated or treated nylon.
Desert dress must protect the skin from the sun’s radiation. (Photo by Alan Halcon)
Other considerations
Remember your legs! Long underwear covered by pants and an outer layer of
nylon wind pants are a good example. Fleece lounge pants make a good
insulation layer as well. Keeping your legs warm can go a long way to keeping
your whole body warm.
In today’s high tech world, it is possible to get all three layers in one garment,
but that is not desirable. You have to wear it all or nothing, and this eliminates
the option to shed layers to regulate your body heat.
When dressing for the cold, the hands, feet and head are often overlooked.
Wear polypropylene-lined Gore-Tex gloves or fleece or knit wool gloves and
under nylon mitts or gloves. Carry a spare pair of thin fleece gloves in a pocket;
these feel warm even when they’re damp.
