Fires > Module 3: Fire Behaviour > Flashcards

Module 3: Fire Behaviour Flashcards

(44 cards)

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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

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A

New fires being started ahead of the main fire

19
Q

Crowning

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A

Fire in the crown of the trees

20
Q

Active Crown Fire

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A

a running fire that also includes the crown fuels

21
Q

Intermittent Crown Fire

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A

an aggressive surface fire with intermittent crown fires

22
Q

Independent Crown Fire

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A

crown fire that spreads without a surface fire

23
Q

Bays

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A

located between Fingers, a marked indentation in the fire

24
Q

Finger(s)

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A

elongated burn area projecting outward from the main body

25
Flank
sides of the fire
26
Head
furthest forward portion of the fire
27
Back
opposite the Head having the lowest rate of spread and intensity
28
Islands
areas of unburned fuels within the body of the fire
29
Point of Origin
exact location where ignition began
30
3 sides of the Fire Behaviour Triangle
1. Fuel (8) 2. Weather (7) 3. Topography (6)
31
Fuel points
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
Weather points
1. Relative Humidity 2. Wind 3. Temperature 4. Precipitation 5. Solar Radiation 6. Cloud Cover 7. Atmospheric Stability
33
Topography points
1. Slope 2. Aspect 3. Elevation 4. Position of Slope 5. Barriers to fire spread 6. Shape of country
34
signs of a stable atmosphere
Stratiform clouds Limited vertical motion of air Cooler temperatures Light Winds
35
signs of an unstable atmosphere
cumuliform clouds increased vertical air movement warmer temps gusty winds
36
Describe Box Canyons, Narrow Canyons and Ridges effects on fire
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
Common Denominators of Fire Behaviours in near misses/tragedies
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
Define: Fire Environment
The surrounding conditions, influences and modifying factors that determine fire behaviour at a given time and location.
39
What does White Smoke mean?
High fuel moisture and Low fire intensity
40
What does Grey Smoke mean?
Fuel is moist and Moderate fire intensity
41
What does Black Smoke mean?
Fuel is dry and High fire intensity
42
What does Copper-Bronze smoke mean?
Fuel is very dry and a High to Severe fire intensity
43
3 types of smoke columns
Drifting Low: Stable atmosphere, lower fire intensity High Vertical Column: Atmosphere unstable, higher fire intensity Sheared off column: Atmosphere unstable, high winds aloft
44
Fire Behaviour Rules of Thumb
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
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