Survival priorities

Human survival priorities are found in the "Rule of Three":

1. Humans cannot survive more than three minutes without air (O2)
2. Humans cannot survive more than three hours exposed to extreme low-temperature
3. Humans cannot survive more than three days without water (H20)
4. Humans cannot survive more than three weeks without food

The Rule of Three should be viewed as generalities. The record is 10 minutes, 17 seconds without air; the crew of a boat lasted 8 days without water; people have survived without food for over 40 days.

In most survival situations, three priorities must be addressed before any other needs are met:

1. Finding or making shelter is the most important because it allows a person to stay protected from the elements.
2. The next priority after finding shelter is water. The length of survival mostly depends upon climate conditions and physical exertion.
3. Food is the third essential for survival. This is especially important during winter, as one has higher calorie-burning needs.

These priorities may change depending upon environmental factors.

A shelter will protect one from potentially disastrous weather, help prevent hypothermia, and allow restful sleep. It will also boost how you feel emotionally, as it will become a base or home. Therefore, in typical survival situations, a shelter should be able to be moved with you, if possible, and be set up quickly. If one spends too much time on a shelter it takes away from other survival tasks.

A shelter should provide a somewhat comfortable place to sleep. To this end, it should account for the following:

* Immovable rocks, animal nests, and other obstacles and hazards should be avoided.
* Dry watercourses may be flat, sandy, and comfortable to sleep on, but they will flood in a storm.
* Sunlight provides warmth (which is not always welcome), and help one to wake up in the morning. However, sunny, open areas are vulnerable to wind.
* Heat transfer: an excessively large or well-ventilated shelter will not retain warmth well.
* Flashing (weatherproofing) to provide protection from elements.
* A cave would be a very useful shelter because it is very resistant to rain water getting in and maintains a constant temperature. Unfortunately, caves can present additional problems such as ground water, dampness and wildlife. Bears also nest in caves, so before selecting a cave to stay in, you should check it for signs of inhabitance.

The simplest and most mobile shelter is a tarp, supported by make-shift frame work or rope. Large leaves, such as ferns or fir branches, can be added to a latticework of branches. Ferns on a shelter provide insect repellent. Branches propped against a fallen tree make a simple and effective refuge, but animals such as ants and snakes may nest under the tree. With some practice, more advanced shelters such as a debris shelter can be constructed without modern tools or implements.