Fire Environment : Wildland Firefighting

Passive crown fire is usually confined to one tree or a small grouping of trees. This stage of crown fire is commonly called __________

torching out

There are three factors that influence the direction a fire will burn: (3)

wind, slope, and condition of the fuel.

0600 to 1000

Fire intensity begins to increase, making fire control more difficult

Sheared smoke column:

Smoke rises straight up Column is sheared off by strong winds aloft Potential for long-range spotting Strong winds could surface.

Fire intensity is the rate of heat energy released during combustion. Fire intensity is measured in two ways: (2)

fireline intensity, flame length

Fire suppression interpretations from flame length ■ Flame lengths less than ___ feet - Fires can generally be attacked at the head or flanks by firefighters using hand tools. Handline should hold fire

4

About ___ % of the energy released from a wild land fire goes into the atmosphere in the convection column

80

Reading the Column of Smoke ■ Leaning smoke column means what ?

A wind-driven fire. Rapid rates-of-spread. Short-range spotting.

A fire burning in uniform fuels on flat ground (with the wind being the only variable) burns with predictable _________ shaped patterns.

elliptical

Another important factor in the arrangement of the fuels are _____ that will allow the fire to move into the tops of the fuels

ladder fuels

________ Sudden increase in fire intensity or rate of spread sufficient to preclude direct control or to upset existing suppression plans.

Blowup

The most important topographic components are, _______ & _________

steepness of slope and aspect

Weather is the most variable component of the fire environment. Weather varies as air masses move through an area. The most important weather components are: (3)

wind, temperature, and relative humidity

________ fuels are usually the "carrier" of the fire, even in timber

Fine

Burning Characteristics Based on Time of Day Time of day 1000 to 1800 _____________

All factors of fire intensity are at their highest. Air is dry; fuels are dry; temperature is high, and winds may be strong

__________ Fire that advances across tops of trees or shrubs more or less independent of surface fire.

Crowning

1800 to 0400

Factors favorable for fire control: winds usually moderate: air is cooler; relative humidity usually increases; and fuel moisture may increase.

There are several factors that influence the fire's rate of spread and burn pattern or shape: (7)

Fire intensity Wind speed Slope Fuel type changes Natural or man-made barriers that stop or slow the spread Spotting

________ intensity is the amount of heat released per foot of fire front per second.

Fireline

Flame length and flame height are different measurements. Flame ___ is measured along the long-axis of the flame, where flame ____ is measured as the distance above the ground

Length, height

________ - Fire spreading rapidly with a well defined head

Running

Foehn or gravity winds can also cause problems. These regional winds are so notorious, they have been given special names such as ________, Mono and Chinook.

Santa Ana

Fire burning with low flame and spreading slowly.

Creeping

If the flame length is over ___ feet, it will pretty much eliminate hand tools as a method of control

four

The most important fuel components are _______ and __________.

fuel moisture, temperature

An ________ crown fire gets its name from the fact that it is not dependent on the surface fire for its energy. The energy that supports this kind of crown fire is developed in the crowns as the fire moves from one crown to another.

independent

There are two types of wind events that can accompany a plume driven fire: (2)

indrafts and downdrafts

In the northern hemisphere there is normally a counter clockwise movement of air as it rises. This means that there will be a higher percentage of spot fires on the ____ side of the fire's head.

left

Crown fires develop in three progressive stages:

passive, active and independent.

A wind driven fire may become a _______ driven fire, when the energy released by the fire takes the convective column to such heights that its force becomes greater than the wind.

plume

Terrain indicators to stay away from (3)

chutes, saddles and narrow canyons

Collapsing smoke column Beware when the column begins to collapse, The ____________ can cause the fire to run in all directions.

downdraft winds

Wildland fires generally burn in __________ patterns. Wind and slope will change the general shape of the ellipse

elliptical

The topographic factors that contribute to fire behavior are (5)

■ Elevation ■ Position on the slope ■ Aspect ■ Shape of the terrain ■ Steepness of slope

Fire Intensity is affected by: (4)

■ Fuel loading ■ Compactness or arrangement of fuels ■ Fuel moisture content ■ Slope and wind speed

_______ the most influential factor when it comes to the fires rate and direction of spread

Wind

_________ : Time of the day when a fire can most easily be controlled. Burning usually remains slow until dawn.

0400 to 0600

Firebrands are moved by four different forces (4)

1) Popping 2) Convection 3) Winds 4) Gravity

There are seven general indicators which can help you predict the possibility of extreme fire behavior

1. Fuel characteristics 2. Fuel moisture 3. Fuel temperature 4. Topography/Aspect 5. Wind 6. Atmospheric stability 7. Fire behavior

The primary factors which affect the ignition of wildland fuels are: 1. _____________ - the smaller/finer they are the easier they ignite 2. ______________ - if they are loose and open they will ignite easier. 3. ________ - The drier they are, the easier they ignite 4. _______ - The warmer the fuel, the less heat it takes to reach its ignition point

1. Size and shape of the fuels 2. Compactness or arrangement of the fuels 3. Fuel moisture content 4. Fuel Temperature

Generally, a wind of just _____ miles per hour can cause rapid rates of spread

10

Another contributing factor in crown fires is crown-to-crown heat transfer. Crown spacing of ____ feet or less (roughly 100 trees per acre) will permit convective and radiant heat transfer to occur at a level of intensity that can maintain a fire spreading through the crowns.

20

If you are told the "1000-hour fuels" are ____ percent, you know that they will burn

20

Spacing of the fuels is another factor controlling crowning. If the spacing of the crowns is less than ___ feet, you have the potential for a crown fire.

20

In most areas when the relative humidity gets below _____ percent or less will allow fine fuels to burn with considerable intensity

25

■ Flame lengths __ to __ feet - Fires are too intense for direct attack on the head with hand tools. Handline cannot be relied upon to hold the fire. Bulldozers, engines, and retardant drops can be effective.

4 to 8

__________ occurs when an area is "peppered" with spot fires, the spot fires start influencing each other, and an area explodes in fire.

Area ignition

_______ - Fire moving away from the head, downhill, or against the wind.

Backing

Well-developed smoke column

Intense burning conditions. Unpredictable fire spread in all directions Look for capped top Strong downburst potential

__________ Fire burning on the surface, but periodically igniting the crown of a single or small group of trees or shrubs before returning to the surface. Although sometimes confused with crowning, this behavior is not as serious as a crown fire, because it lacks a strong horizontal travel

Torching

_________ is a major factor in how fast and intensely a fire will bum. Wind pushes a fire to burn in an oval pattern

Wind

A _____ crown fire is also dependent on the surface fire, but there is much more transfer of heat from one burning crown to the unburned crowns of other trees

active

Changing smoke column: Beware when the column begins to _____ or ______

change color or rotate.

■ Flame lengths over ___ feet - Crowning, spotting and major fire runs are probable. Control efforts at the head of the fire are ineffective.

11

A 5 mile-per-hour wind will impact rate of spread in the same way as a ___ percent slope

50

Combustion usually occurs at about ____ degrees in wildland fuel.

500

Spread -The movement of the fire, usually measured by the rate of spread. Rate of spread has at time component (e.g., three mile per-hour; two chains-per-hour; etc.). A chain is a surveying term. A chain is feet ____ in length.

66

"10-hour fuels" with a fuel moisture content below ___ percent are an indicator of dry conditions

7

Probability of ignition is the percentage of firebrands "launched" that actually start fires. When the probability of ignition is ___ percent, it means that of ten glowing firebrands that land on receptive fuels, seven of them will, in fact start a new fire.

70

■ Flame lengths ___ to ___ feet - Fires may present serious control problems: torching, crowning, and spotting. Control efforts at the head will probably be ineffective.

8 to 11

Typical energy release from wildland fuels is about ______ BTUs per pound.

8,000

The fuel components that affect fire behavior are: (8)

■ Fuel loading ■ Size and shape of the fuel ■ Compactness ■ Horizontal continuity ■ Vertical continuity ■ Chemical content ■ Fuel moisture ■ Fuel temperature

For an active or independent crown fire to sustain its run, several conditions are needed: (5)

■ Low fuel moisture ■ Relatively close crown spacing ■ Intense surface fire ■ Strong winds and/or steep slopes. ■ The ability to spot ahead in discontinuous fuels

The weather related factors that influence fire behavior (5)

■ Temperature ■ Relative humidity ■ Atmospheric stability ■ Wind speed and direction ■ Precipitation