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Wildland and Ground Fires

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The Wildland Fire Triangle

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3

Fuel• Subsurface – under the ground

• Surface – up to 6’ above the ground

• Aerial – more than 6’ above the ground

• Fine - Includes dried vegetation such as twigs, leaves, needles, grass, moss, light brush and

duff– Aids the ignition of heavier fuels

• Heavy - Includes large brush, heavy timber, stumps, branches, slash and dead timber on the

ground– Do not spread a fire as rapidly as fine fuels– Can burn with a high intensity

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5

Other Fuel Characteristics

• Size and Shape• Compactness• Continuity• Volume/Quantity• Moisture Content

* Will determine rate of ignition, fire spread and intensity

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6

Weather

• Moisture– 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 (Varies with the time of day and year)

– Precipitation

• Wind• Air Temperature

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“The 10am Concept”

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Topography

• Slope• Aspect (N, E, S, W)• Valleys• Ridges• Canyons• Natural barriers eg. streams and lakes

• Manmade barriers eg. Highways

* May increase or impede fire behaviour, rate of spread

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Anatomy of a Wildland Fire

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Anatomy of a Wildland Fire (2)

• 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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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– Portable pumps– Booster tanks from apparatus– Aircraft

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Removing Fuel (1 of 2)

• Removal of fine fuels:– Fire broom– Steel fire rakes– McLeod fire tool

• Removal of heavier brush:– Adze– Pulaski axe – Hand saws, chainsaws– Tractors, plows, and bulldozers

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Removing Fuel (2 of 2)

• 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• Smothering

– Most commonly used when overhauling the last remnants of a wildland fire

– Earth is thrown on smoldering vegetation. – Not as useful during the more active phases of a fire

• Compressed air foam systems (CAFS)– 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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Wildland Urban Interface

• The mixing of wildland with developed areas • Wildland fires regularly ignite buildings and

become structure fires. • Fires in this zone present a significant life

safety hazard. • Many areas do not have adequate municipal

water systems.

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Fire Intensity Rankings

(courtesy BC Forest Service http://bcwildfire.ca/FightingWildfire/firerank.htm)

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Rank 1Smouldering ground or

creeping surface fire

Rank 2Low vigor surface fire

Rank 3Moderately vigorous

surface fire, “candling”

Rank 4Highly vigorous

surface fire, torching (or passive crown fire)

Rank 5Extremely vigorous

surface fire, or active crown fire

Rank 6Blow up/Conflagration,

Extreme fire behaviour

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The End

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