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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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