5-1. A properly constructed and utilized fire is one of the best tools an isolated person has. The use of fire supports several different survival needs and provides many other benefits. Fire—
- Provides several ways to signal recovery forces with light and smoke and increases the isolated person’s presence in the area with multiple well-placed fires. Fires allow personnel to multi-task while fire acts as a passive signal to recovery forces.
- Provides a sustained source of heat that reduces energy required for the body to maintain its temperature. Consequently, isolated persons require fewer calories and less food.
- Enables the most effective method of water purification, boiling.
- Dries wet clothing and prevents cold injuries such as immersion foot, frostbite, and hypothermia.
- Provides coals and flame to improvise tools.
- Emits heat and smoke to preserve and cook food for consumption.
- Repels mosquitos and dangerous animals.
- Provides the requisite heat to sterilize items for medical purposes.
- Boosts morale by providing comfort, peace of mind, entertainment, and companionship.
5-2. Fire is a very useful tool that will require knowledge of how to build, use, and maintain a fire under the most austere and inhospitable conditions. Fire is used with caution to prevent damage and injury to isolated persons and their surroundings.
Fire Burning Principles
5-3. To build a fire, it helps to understand the following basic principles of a fire:
- Fuel (in a nongaseous state) does not burn directly.
- When heat is applied to a fuel, it produces a gas. This gas, combined with oxygen in the air, burns at a sustained rate as long as there is fuel to supply the gas.
- Understanding the fire triangle is very important in constructing and maintaining a fire. The three sides of the triangle represent heat, oxygen, and fuel. If any of these are removed, the fire will go out. The correct ratio of these components is very important for a fire to burn at its greatest capacity (see figure 5-1 on page 5-2). Manipulating the structure of a poorly burning fire is an effective way to adjust the ratio of heat, oxygen, and fuel to reach a desired state.
Selecting and Preparing a Fire Site
5-4. Determining a good site to build a fire is an often overlooked but important step in effectively using a fire. Isolated persons should select a site that provides a good foundation for building a fire and prepare it to support the isolated person’s needs. Considerations include—
- Terrain and climate.
- Materials and tools available for fire building.
- Time available for fire building.
- Expected duration of isolation.
- Purpose(s) for the fire.
- Security risks that a fire may cause.
- Requirement to direct heat in a desired direction.
5-5. Fire sites should meet the following basic criteria:
- Flat, dry area to construct fire and accomplish fire-related activities.
- Protected from the wind.
- Located near isolated person’s shelter or living area.
- Near a fuel supply to maintain the fire.
- Away from snow laden trees.
5-6. To prepare a fire site—
- Clear the ground of fallen leaves, vegetation, and duff; expose 3 feet (1 meter) in diameter of soil at a minimum to prevent the fire from spreading along the ground.
- Porous rock is removed from the fire site, which is at risk of exploding from the heat of the fire.
- Level the area that the fire is to be constructed upon, if sloped, to prevent fuel from sliding off the fire.
- In deep snow where the soil cannot be reached, green logs are used as a base to build the fire on to prevent the coals from melting a hole through the snow pack and away from isolated persons. In the cold green logs up to the size of a soda can are easily broken. Pieces are stacked in two layers, the top being perpendicular to the bottom to a size that contains the entirety of the intended fire.
- Construct a fire reflector if desired; this task is more easily accomplished during the preparation phase before the fire becomes hot.
Fire Reflector
5-7. Fire reflectors are used to maximize the heat produced from the fire by directing in a desired direction and protecting the heat from being displaced by the wind. Reflectors can be constructed of nonporous rock or stack of logs most effectively made of green wood (see figure 5-2). When located at the opening of a shelter, the heat is directed into the enclosure to elevate the temperature of the living area.
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