Wildland Fire Behavior
I - An Introduction

Objectives
 Identify the environmental factors which
govern the behavior of wildland fires.
 Describe four methods of heat transfer.
Upon completion of this unit, the student
will be able to:

The Origin of Fire
All fires have at least one thing
in common:
An original ignition point.

The Fire Triangle
Three elements must be present in the correct
proportions for an ignition to occur.
Fuel Heat
Oxygen

The Fire Triangle
Remove any one of these elements,
Fuel Heat
Oxygen
and the fire goes out.

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Components of the Wildland Fire Environment
WEATHER
TOPOGRAPHY
FUELS

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WEATHER
 Temperature
 Relative Humidity
 Atmospheric Stability
 Wind Speed and Direction
 Precipitation
Components of the Wildland Fire Environment

Components of the Wildland Fire Environment
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TOPOGRAPHY
 Elevation
 Position on Slope
 Aspect
 Shape of Country
 Steepness of Slope

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Components of the Wildland Fire Environment
FUELS
Fuel Loading
Size and Shape
Compactness
Horizontal Continuity
Vertical Continuity
Chemical Content

Fire Triangle
 Heat
– Types of heat transfer
 Radiation
 Conduction
 Convection
 Mass Transfer
– Preheating of fuels
 Fuel Temperature
 Sun vs. Shade

Heat Transfer
For combustion to be sustained and for
fires to spread, heat must be transferred
from one fuel particle to the next. This
happens 3 different ways:
Conduction
Convection
Radiation

Heat Transfer Methods
CONDUCTION:
Transfer of heat from one molecule to another.
CONVECTION:
Transfer of heat by movement of air.
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RADIATION:
Transmission of heat by electromagnetic waves.

Conduction
Conduction is the transfer of heat from one
particle of fuel directly to another.
Wood is a poor conductor of heat, so
conduction is the least important means of
heat transfer in terms of wildland fire behavior.

Convection
Convection is the process of “hot air
rising”. It is what makes smoke columns
rise and assists in upslope fire runs.
It is potentially
the most
dangerous
of the three heat
transfer methods.

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Transport of Firebrands by
Convection

Radiation
Radiation is the transfer of energy through
space, in the form of light and heat.
Radiant heat will dry and potentially
ignite surrounding fuels.

Mass Transfer
Heat transported in the form of
firebrands.

Transport of Firebrands by Wind
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WIND

Transport of Firebrands by Gravity
01-18-S290

Fire Triangle
 Oxygen (air, wind)
– Needed for
combustion
– Contributes to the
rate and direction of
spread (wind)
– Contributes to
spotting problems