Wildland Firefighting (3rd Edition)
Chapter 1-Wildland Fire Behavior:  Fuel, Weather, Topography
Test Review

• Fire is actually a by-product of a larger process called combustion.
• Rapid oxidation occurs in either smoldering or steady-state phases.
• Fuels exist in solid, liquid, and gas form.
• Only fuels in gas form will burn.
• Pyrolysis is a chemical change caused by the action of heat.
• Heat generated by a fire evaporates the moisture in the fuel and heats the fuel to ignition temperature.
• Heat transfer takes place by conduction, convection, and radiation.
• Heat transfer by conduction has limited effect on the spread of wildland fires.
• Materials that rise into the atmosphere by convection may fall back to earth as much as a mile downwind, starting spot fires ahead of the main fire.
• Direct flame contact preheats fuels upslope.
• Heat waves, also called infrared rays, radiate in all directions from their source and travel through space until partially or totally absorbed by an opaque object.
• Radiated heat is one of the major sources of fire spread in wildland fires.
• Radiant heat is responsible for many burn injuries in wildland fires.
• Combustion can be interrupted by removing the fuel, removing oxygen, removing heat energy, or inhibiting flame-producing chemical reactions.
• Heat from catalytic converters on cars can start grass fires.
• Clearing a space of all surface fuels down to the mineral soil is a common way of controlling wildland fires.
• All forms of vegetation, alive or dead, are fuel for wildland fires.
• The NFDRS classifies fuels as grasses, brush, timber (trees), or slash.
• Grasses are either annual (rye, wild oats) or perennial (saw grass, various tundra species).
• Solar heating alone will not cause ignition, but will facilitate ignition.
• Water is present in the environment in the form of precipitation, ground moisture, and humidity.
• Fuel moisture varies according to plant species, age of plant, and weather conditions.
• One system of fire behavior prediction is based on weather cycles and fuel types.
• Fuels on North-facing slopes are less affected by solar heating.
• Fuels on North-facing slopes are less affected by solar heating, so their daytime moisture content is generally not as low as fuels on level or South-facing slopes.
• Wildland fuels are based on position such as subsurface, surface, and aerial.
• Subsurface fuels are roots, peat, duff, and partially decomposed organic matter.
• Surface fuels include needles, leaves, twigs, grass, field crops, brush up to 6 feet in height, downed limbs, logging slash, and small trees.
• Twigs, needles, and grass are sometimes referred to as flashy fuels.
• Ladder fuels include hanging pine boughs, tree moss, tall grasses, brush beneath aerial fuels, and downed limbs or logs in contact with surface fuels.
• Aerial fuels are physically separated from the ground surface.
• Aerial fuels include brush over 6 feet tall, live/dead leaves and needles on tree limbs, branches, snags, hanging moss, and lichen.
• Fuel load is commonly reported in terms of tons of fuel available per acre.
• Fuel types are classified according to fuel loading (volume), fuel bed depth (position), and moisture of extinction.
• Continuous fuels are spread evenly over an area.
• Patchy fuels are separated by bare ground such as grass growing in clumps.
• Fuel compaction is the amount of space between the fuel molecules,
• The rate of heat transfer and changes in moisture content is directly related to the size of the fuel.
• Fuels are described as light, medium, or heavy.
• Light fuels, also called fine, flashy, or flash fuels, are short grass and light brush up to 2 feet that burn rapidly.
• More firefighters are killed in light fuels that any other type.
• Weather is a key factor in firefighter safety and survival on the fireline because of its influence on fire behavior.
• Weather is the most changeable factor in regards to wildland fire behavior.
• The troposphere is the lowest layer of the atmosphere and is responsible for most ground level atmospheric conditions.
• Unstable air encourages the vertical movement of air and tends to increase fire activity.
• Stable air discourages vertical movement of air and reduces fire activity.
• Haze and smoke tend to rise in unstable air and spread horizontally in stable air.
• Fires may suddenly blow up and become erratic in unstable atmospheres.
• Air that is cooled by the earth's surface at night forms surface inversions, also called a night inversion.
• Marine inversions are common in the summer, caused by cool, moist air spreading inland in a layer.
• The top of an inversion layer is called the thermal belt.
• Thunderstorm cloud-to-ground lightning and downdrafts can greatly influence fire behavior.
• Visual indicators of thunderstorms include:  Tall, building cumulus clouds, cauliflower-shaped cloud tops, clouds with dark, flat bases, rain that evaporates before reaching the ground, and anvil-shaped clouds with fuzzy appearance.
• Adiabatic cooling is loss of temperature when heat is neither gained nor lost by mixing with the surrounding air.
• Relative humidity is the percentage of moisture relative to the total amount of moisture that the volume of air can hold.
• Wind direction is identified as the direction from which the wind is blowing.
• Local winds are a by-product of daily heating and cooling patterns, also called diurnal cycle.
• Heating of hilly or mountainous terrain causes upslope winds, likewise, cooling causes downslope winds.
• Heating of flat terrain can cause whirlwinds or dust devils.
• Frontal winds occur at the front of warm or cold air masses.
• Gradient winds flow from areas of high barometric pressure to areas of lower pressure.
• Gravity winds, also called foehn winds, result from air being forced over mountain ridges by convection or high barometric pressure.
• Convective winds are caused by the localized heating of air that expands and rises while cooler, denser air descends to replace it.
• Examples of convective winds include:  Slope winds, valley winds, land/sea breezes, and thunderstorm winds.
• Steep valleys, chutes, drainages, and similar terrain are sometimes referred to as chimneys.
• Firewhirls are usually formed on the leeward side of elevated terrain features.
• A direct attack on firewhirls is not recommended.
• Wind and fuel moisture are the two most important weather-related elements of wildland fire behavior.
• The features of the earth's surface, both natural or constructed, are termed topography.
• Fire usually move faster uphill than downhill.
• The aspect of a slope is the compass direction in which the slope faces.
• A fireline located just beyond a ridge can be very effective.
• A steep V-shaped drainage is called a chute, also called gullies.
• A depression between two hilltops is called a saddle, also called arroyos.
• Fuel, weather, and topography are major factors affecting wildland fire behavior.
• The rate that a fire extends its horizontal dimensions is termed Rate of Spread.
• Rate of Spread is usually measured in feet per minute.
• Crowning is burning through the tops of trees or shrubs, more of less independently of the surface fire.
• The amount of heat and fire produces over time and distance is the fire's intensity, also called fireline intensity.
• A blowup is sometimes considered to be the wildland equivalent to a flashover.