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Fires > Module 3: Fire Behaviour > Flashcards

Module 3: Fire Behaviour Flashcards

1
Q

Define: Fire Behaviour

A

The manner in which a fire reacts to fuel, weather and topography.

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2
Q

What are the three reasons it is vital to understand the principles of fire behaviour?

A
  1. Personal Safety
  2. Suppression
  3. Use as a prescriptive management tool
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3
Q

Fire is the simultaneous release of what?

A

Heat, light and flame caused by the rapid oxidization of fuel

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4
Q

What 3 things does a forest fire produce?

A
  1. Carbon dioxide
  2. water vapour
  3. heat
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5
Q

3 factors required for fire to perpetuate

from Van Wagner circa 1983

A
  1. sufficient supply of continuous fine fuels
  2. fuels must be dry enough for open flame
  3. must be an ignition source
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6
Q

2 limiting factors in fire spread

Van Wagner circa 1983

A
  1. needs sufficient heat from fire to warm unburned fuels to ignition temperature
  2. enough fuel to support a solid flame
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7
Q

What are the 3 phases of combustion

A
  1. Preheating Phase: unburned fuels in front heated to critical temp of 350 degrees C
  2. Distillation Phase: at 350 degrees and up volatile gases form from the solid fuels and ignite in oxygen, producing solid flame.
  3. Charcoal Phase: not enough vapour to support open flame and residual solid fuels smoulder away
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8
Q

What is pyrolysis?

A

when solid fuels are heated beyond the critical temp of 350 and are broken down into a volotile vapour

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9
Q

4 zones of pyrolysis

A
  1. Ash
  2. Char
  3. Pyrolysis
  4. Unburnt Fuel
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10
Q

What are the 3 sides of the fire triangle

A

Oxygen, Heat, Fuel

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11
Q

How to suppress a fire via Oxygen, Heat or Fuel?

A

O2: cover the fuel with dirt
Heat: cool the fuels with water or chemicals
Fuels: separate the fuels from the fire line

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12
Q

what are the 4 types of heat transfer (think campfire)

A
  1. Convection: natural upward movement of hot air
  2. Radiation: heat moved in straight lines with the speed of light from a warmer to cooler surface (preheating)
  3. Conduction: movement of heat through a solid surface (wood is a poor conductor)
  4. Embers: heat movement form wind carrying embers ahead of fire
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13
Q

The 3 types of fires?

A

Crown Fire: fire involving the tree crowns
Surface Fire: fire involving surface fuels only (often associated with intermittent or active crown fires)
Ground Fire: fire involving ground fuels (lingering in old stumps or duff)

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14
Q

Define Smouldering

A

Barely spreading fire with no flames.

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15
Q

Define Creeping

A

Low flames spreading slowly

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16
Q

Define Running

A

Rapidly spreading surface fire with a well developed front

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17
Q

Torching/Candling

A

Single or small group of trees flaring up

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18
Q

Spotting

A

New fires being started ahead of the main fire

19
Q

Crowning

A

Fire in the crown of the trees

20
Q

Active Crown Fire

A

a running fire that also includes the crown fuels

21
Q

Intermittent Crown Fire

A

an aggressive surface fire with intermittent crown fires

22
Q

Independent Crown Fire

A

crown fire that spreads without a surface fire

23
Q

Bays

A

located between Fingers, a marked indentation in the fire

24
Q

Finger(s)

A

elongated burn area projecting outward from the main body

25
Q

Flank

A

sides of the fire

26
Q

Head

A

furthest forward portion of the fire

27
Q

Back

A

opposite the Head having the lowest rate of spread and intensity

28
Q

Islands

A

areas of unburned fuels within the body of the fire

29
Q

Point of Origin

A

exact location where ignition began

30
Q

3 sides of the Fire Behaviour Triangle

A
  1. Fuel (8)
  2. Weather (7)
  3. Topography (6)
31
Q

Fuel points

A
  1. Fuel Type
  2. Moisture Content
  3. Quantity
  4. Size of Fuel
  5. Arrangement of Fuel
  6. Fuel Continuity
  7. Fuel Chemistry
  8. Seasonal Condition
32
Q

Weather points

A
  1. Relative Humidity
  2. Wind
  3. Temperature
  4. Precipitation
  5. Solar Radiation
  6. Cloud Cover
  7. Atmospheric Stability
33
Q

Topography points

A
  1. Slope
  2. Aspect
  3. Elevation
  4. Position of Slope
  5. Barriers to fire spread
  6. Shape of country
34
Q

signs of a stable atmosphere

A

Stratiform clouds
Limited vertical motion of air
Cooler temperatures
Light Winds

35
Q

signs of an unstable atmosphere

A

cumuliform clouds
increased vertical air movement
warmer temps
gusty winds

36
Q

Describe Box Canyons, Narrow Canyons and Ridges effects on fire

A

Box Canyon: strong updraft could be created increasing the intensity and rate of spread
Narrow Canyon: radiant heat could warm fuels opposite of fire and allow easier spotting
Ridge: Winds flow like water around and over ridges and can create eddies on lee sides allowing fire to be pushed down hill

37
Q

Common Denominators of Fire Behaviours in near misses/tragedies

A
  1. small or quiet sectors on larger fires
  2. relatively light fuels
  3. unexpected wind shifts, gusts or squalls
  4. upslope fire run: chimney, narrow valley or steep slope
38
Q

Define: Fire Environment

A

The surrounding conditions, influences and modifying factors that determine fire behaviour at a given time and location.

39
Q

What does White Smoke mean?

A

High fuel moisture and Low fire intensity

40
Q

What does Grey Smoke mean?

A

Fuel is moist and Moderate fire intensity

41
Q

What does Black Smoke mean?

A

Fuel is dry and High fire intensity

42
Q

What does Copper-Bronze smoke mean?

A

Fuel is very dry and a High to Severe fire intensity

43
Q

3 types of smoke columns

A

Drifting Low: Stable atmosphere, lower fire intensity
High Vertical Column: Atmosphere unstable, higher fire intensity
Sheared off column: Atmosphere unstable, high winds aloft

44
Q

Fire Behaviour Rules of Thumb

A
  1. Temp > or = RH: crossover and control problems likely
  2. RH < or = 20%: extremely dry fine fuel
  3. FFMC > or = 90: fast moving surface fire
  4. 101 - FFMC = moisture content % of fine fuels (ex: 101 - 93 = 8% mc)
  5. ISI > or = 10: fuels burn quickly, Black Spruce likely to crown
  6. BUI > or = 60: med-heavy fuels cause problems in fire behaviour
  7. DC > or = 300: difficult to control and possible holdover fires

Fires (8 decks)

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