Post on 13-Jan-2016
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Wildland and Ground Fires
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Objectives (1 of 3)
• Define the terms wildland and ground fires.
• Define light fuels, heavy fuels, subsurface fuels, surface fuels, and aerial fuels.
• Describe how weather factors and topography influence the growth of wildland fires.
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Objectives (2 of 3)
• Define the parts of a wildland and ground fire.
• Describe how wildland and ground fires can be suppressed.
• List the hazards associated with wildland and ground firefighting.
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Objectives (3 of 3)
• Describe the personal protective equipment needed for wildland firefighting.
• Explain the problems created by the wildland urban interface.
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What are Wildland Fires? (1 of 3)
• Defined by NFPA:– Unplanned and uncontrolled fires burning
in vegetative fuel that sometimes includes structures.
• Can consume grasslands, brush, and trees of all sizes
• Incidence varies from season to season.
• Referred to by different terminology
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What are Wildland Fires? (2 of 3)
• Ground cover fires burn loose debris on the surface of the ground.
• Some fire departments respond to more wildland and ground fires than to structural fires.
• Many structural fire fighters are called on to extinguish wildland and ground fires at some point.– Must have proper training
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What are Wildland Fires? (3 of 3)
• Large wildland fires are handled by specialized agencies.– Each state has an agency designated to
coordinate wildland firefighting. – There are federal agencies that are
responsible for coordinating firefighting activities at large incidents.
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Wildland and Ground Fires and the Fire Triangle
• Wildland and ground fires require the same three elements as structural fires.– Fuel, oxygen, and heat
• In wildland and ground fires the conditions under which fuel, oxygen, and heat come together to produce a fire are different.
• Weather conditions have a great impact on wildland fire behavior.
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The Wildland Fire Triangle
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Fuel (1 of 2)
• Primary fuel is area vegetation.• Amount of fuel in an area ranges from
sparse grass to heavy underbrush and large trees.
• Some fuels ignite readily and burn rapidly when dry.
• Others are harder to ignite and burn more slowly.
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Fuel (2 of 2)
• Vegetative fuels can be located:– Under the ground (roots)– On the surface (grass and fallen leaves)– Above the ground (tree branches)
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Fine Fuels
• Includes dried vegetation such as twigs, leaves, needles, grass, moss, and light brush
• Ground duff – Partly decomposed organic material on a
forest floor
• Main type of fuel in ground cover fires • Aid the ignition of heavier fuels
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Heavy Fuels
• Includes large brush, heavy timber, stumps, branches, and dead timber on the ground
• Slash– Consists of the leftovers of a logging operation
• Do not spread a fire as rapidly as fine fuels• Can burn with a high intensity
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Subsurface Fuels
• Located under the ground
• Roots, moss, duff, and decomposed stumps
• Fires involving subsurface fuels are hard to locate and extinguish.
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Surface Fuels
• Located close to the surface of the ground
• Include grass, leaves, twigs, needles, small trees, and slash
• Brush less than 6' above the ground
• Sometimes called ground fuels
• Involved in ground cover fires
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Aerial Fuels
• Also called canopy fuels
• Located more than 6’ above the ground
• Usually trees
• Includes tree limbs, leaves and needles on limbs, and moss attached to the tree limbs
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Other Fuel Characteristics
• May determine how quickly the fuel ignites, how rapidly it burns, and how readily it spreads to other areas
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Size and Shape of Fuel
• Size and shape of a fuel influences how it burns.
• Fine fuels burn more quickly than heavy fuels.
• Requires less heat to reach their ignition temperature
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Fuel Compactness
• Influences the rate at which a fuel will burn
• Air cannot circulate in and around fuels that are tightly compacted.
• Subsurface fuels burn more slowly than aerial fuels.
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Fuel Continuity
• Refers to the relative closeness of wildland fuels
• Are close together or touch each other• Allows fire to spread from one area of fuel to
the next• Have a sufficient supply of air to support rapid
combustion • Burn much more rapidly than fuels that are
compact
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Fuel Volume
• Refers to the quantity of fuel available in a specific area
• Amount of fuel in a given area influences the growth and intensity of the fire.
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Fuel Moisture
• Refers to the amount of moisture contained in a fuel
• Amount of moisture in a fuel influences the speed of ignition, the rate of spread, and the intensity of the fire.
• Fuels with high moisture content will not ignite and burn as readily.
• Fuel moisture varies with the amount of rain that has fallen.
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Oxygen
• Oxygen is needed.• Not usually an important variable in the
ignition or spread of the fire.• Air movement influences the speed with
which a fire moves. • Wind speeds the process of combustion
and influences the direction the fire travels.
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Heat
• Sufficient heat must be applied to fuel in the presence of adequate oxygen to produce a fire.
• Three categories of factors may ignite wildland and ground fires:– Natural causes– Accidental causes– Intentional causes
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Weather
• Weather conditions have a large impact on the course of a wildland fire.
• Moisture
• Wind
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Moisture (1 of 2)
• Relative humidity – Ratio of the amount of water vapor present
in the air compared to the maximum amount the air can hold at a given temperature
– A major factor in the behavior of wildland and ground fires
– Varies with the time of day and year
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Moisture (2 of 2)
• Precipitation– Moisture falling from the sky helps to
increase the relative humidity. – Absorbed by plants
• Makes them less susceptible to combustion
– When there is adequate precipitation, fire risk is lower.
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Wind
• Has the ability to move a fire at great speed
• Effect of wind on a wildland and ground fire is similar to fanning a fire to help it burn more rapidly
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Topography (1 of 2)
• Refers to the changes of elevation in the land, the position of natural, and manmade features
• Has a great impact on the fire behavior • When fires burn on flat land, much of the fire
heat will rise into the air. • When the elevation rises in the direction the
fire is traveling, the fire heat ignites a greater quantity of fuel and increases the speed of fire spread.
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Topography (2 of 2)
• Natural barriers, such as streams and lakes, may help contain fires.
• Manmade barriers such as highways also make it easier to contain a fire.
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Anatomy of a Wildland Fire (1 of 4)
• Area of origin– Location where fires begin
• Head of the fire – Main or running edge of a fire – Part of the fire that spreads with the
greatest speed
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Anatomy of a Wildland Fire (2 of 4)
• Heel of the fire or the rear of the fire – Side opposite the head of the fire, often
close to the area of origin
• Finger – Narrow point of fire caused by a shift in
wind or a change in topography – Can grow and produce a secondary
direction of travel for the fire
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Anatomy of a Wildland Fire (3 of 4)
• Pocket– A dangerous place for fire fighters because
it is an area of unburned fuel surrounded on three sides by fire
• Island – An unburned area surrounded by fire
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Anatomy of a Wildland Fire (4 of 4)
• Spot fire – New fire that starts outside areas of the
main fire
• Green – Area of unburned fuels
• Black – Areas that have already been burned
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Methods of Extinguishment
• Cooling the fuel
• Removing the fuel
• Smothering
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Cooling a Wildland Fire
• Water is used to cool.– Backpack pump extinguishers– Booster tanks from apparatus– Aircraft
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Removing Fuel (1 of 2)
• Removal of fine fuels can be accomplished with:– Fire broom– Steel fire rakes– McLeod fire tool
• Removal of heavier brush:– Adze– Pulaski axe
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Removing Fuel (2 of 2)
• Sometimes saws are used to remove heavy brush and trees from the fire. – Hand saws to gasoline powered chainsaws– Tractors, plows, and bulldozers
• Backfiring – When properly set can burn an area of
vegetation in front of the fire, thereby creating an area devoid of vegetation
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Removing the Oxygen (1 of 2)
• Smothering – Most commonly used when overhauling the
last remnants of a wildland and ground fire – Earth is often thrown on smoldering
vegetation to prevent flare-ups. – Not as useful during the more active
phases of a fire
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Removing the Oxygen (2 of 2)
• Compressed air foam systems (CAFS) – Combines foam concentrate, water, and
compressed air to produce a foam – Sticks to vegetation and structures in the
fire’s path – When the heat of the fire reaches the
foam, it absorbs the heat and breaks down the foam.
– This cools the fuel.
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Types of Attacks
• Direct attack
• Indirect attack
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Direct Attacks
• Mounted by containing and extinguishing the fire at its burning edge
• Fire fighters might smother the fire with dirt, use hoses to apply water to cool the fire, or remove fuel.
• Dangerous to fire fighters because they must work in smoke and heat close to the fire
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Indirect Attacks
• Most often used for large fires that are too dangerous to approach through a direct attack
• Mounted by building a fire line • Can be mounted using hand tools or by using
mechanized machinery • Most appropriate when the topography is so
rough that a direct attack is dangerous or impossible
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Priorities of Attack
• IC must assess and evaluate the priorities for preserving lives and property before determining how to attack a wildland fire.
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Safety in Wildland Firefighting
• Fighting wildland and ground fires is hazardous duty.
• Shares many of the hazards of structural firefighting plus additional hazards:– Driving, falls, smoke and fire, and falling
trees
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Hazards of Wildland Firefighting (1 of 2)
• Driving in rough terrain– Risk of rollover
• Working in rough terrain– Risk of falls
• Burns and smoke inhalation– Wear PPE – Use SCBA in conditions where needed
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• Falling trees– Trees of all sizes can fall with little warning.
• Electrical hazards– Wires that drop on vegetation may ignite. – Difficult to see at night and in smoky
conditions
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Hazards of Wildland Firefighting (2 of 2)
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Personal Protective Equipment
• One-piece jumpsuit, or a coat, shirt, and trousers – Meet the requirements of NFPA 1977– Garments should be constructed of a fire-resistant
material like Nomex®– Wear an approved helmet with a protective
shroud, eye protection, gloves, and protective footwear.
– Respiratory protection• Filter mask
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Fire Shelters
• Lifesaving piece of equipment
• Thin reflective foil layer attached to a layer of fiberglass
• Designed to reflect about 95% of a fire’s radiant heat for a short period of time
• Fire fighters use their fire shelters when unable to reach safety in time.
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Wildland Urban Interface (1 of 2)
• The mixing of wildland with developed areas
• Creates a massive problem for fire departments in many parts of the country
• Wildland fires regularly ignite buildings and become structure fires.
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Wildland Urban Interface (2 of 2)
• Wildland urban interface – Explain the mixing of wildland with developed
areas – Area where undeveloped land with vegetative
fuels is mixed with manmade structures
• Fires in this zone present a significant life safety hazard.
• Many areas do not have adequate municipal water systems.
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Summary (1 of 2)
• Wildland fires are unplanned and uncontrolled fires burning in vegetative fuel that sometimes includes structures.
• Fire fighters need to understand the factors that cause fire ignition and affect the growth and spread of wildland fires.
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Summary (2 of 2)
• Growth of the fire is influenced by weather factors and by the topography of the land.
• Assess and evaluate the priorities for preserving lives and property.
• The wildland urban interface creates a massive problem for fire departments.
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