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Fire science, flashovers & backdraughts > Fire science > Flashcards

Fire science Flashcards

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1
Q

Fire science

What is the definition of combustion?

A

An irreversible chemical reaction producing heat and light

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2
Q

Fire science

Name the things required to make up the ‘triangle of fire’?

A
  • fuel
  • heat
  • oxygen
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3
Q

Fire science

Name the three states in which matter can exists?

A
  • solid
  • liquid
  • gas
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4
Q

Fire science

Name the SI unit that measures heat energy?

A

joules (J)

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5
Q

Fire science

Heat is spread in three ways, what are they?

A
  • convection
  • conduction
  • radiation.
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6
Q

Fire science

What is the term used to descried a substance that contain oxygen “Lock-up” within its structure which is then released to allow combustion?.

A

Oxidising agent

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7
Q

Fire science

To extinguish a fire it is necessary to break one of the legs on the triangle of fire how can this be achieved?

A
  • cooling
  • starving
  • smothering.
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8
Q

Fire science

What is a Flash Point?

A

The lowest temperature at which sufficient vapours are produced for a momentary flash to occur when an ignition source is introduced. But there are insufficient vapours for it to continue burning once the ignition source is removed

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9
Q

Fire science

What is Fire Point?

A

The lowest temperature at which sufficient vapours are produced for the fuel to ignite and continue to burn once an ignition source is introduced.

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10
Q

Fire science

What is meant by the term Auto-ignition temperature?

A

The lowest temperature at which a fuel will ignite and continue to burn without the need for an ignition source

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11
Q

Fire science

What do the initials LEL stand for and explain there meaning?

A

lower explosive limit.

Below a fuels LEL it will be too lean to burn

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12
Q

Fire science

What do the initials UEL stand for and explain there meaning?

A

Upper Explosive Limit.

Above this the mixture will be too fuel rich to burn

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13
Q

Fire science

Describe what the ‘flammable range’ of a fuel is?

A

The ‘flammable’ range is between the LEL and the UEL and it is the percentage mixtures of fuel and air that are capable of being ignited

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14
Q

Fire science

Describe the 4 classes of fire, class A,B,C and D ?.

A
  • Class A - Carbonaceous
  • Class B - Liquids and Liquefiable Solids
  • Class C - Gases and Liquefied Gases
  • Class D - Metals
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15
Q

Fire science

What colour is a “diffused” flame?

A

red & yellow

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16
Q

Fire science

What is meant by the term ‘pyrolisis’?

A

Pyrolisis is the decomposition of a substance by heat which can produce flammable gases

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17
Q

Fire science

Define a flashover?

A

A sudden and sustained transition of a growing fire into a fully developed fire

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18
Q

Fire Science

What are the signs of a flashover?

A
  • Intense heat forces crews low
  • Flames in gas layer
  • Lowering of neutral plan
  • All exposed surfaces pyrolising
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19
Q

Fire Science

What actions should you take when dealing with a flashover?

A
  • Pulse spray into ceiling , cool gases
  • Stay low
  • Consider withdrawing and fire fight from out side
  • Consider ventilation
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20
Q

Fire science

What are the signs of a flashover?

A
  • intense heat forces crews low
  • flames in gas layer
  • lowering of neutral plan
  • all exposed surfaces pyrolising
21
Q

Fire science

What actions should you take when dealing with a flashover?

A
  • pulse spray into ceiling , cool gases
  • stay low
  • consider withdrawing and fire fight from out side
  • consider ventilation
22
Q

Fire Science

What are the external signs of back draught ?

A
  • Fire burning for some time
  • Fire gases being pushed out under pressure from gaps
  • Windows blackened with no visble sign of flame
  • Fire gases (smoke) pulsing out from gaps
23
Q

Fire Science

What are the internal signs of backdraught ?

A
  • Low neutral plane
  • Darkening of fire gases
  • Inrush of air & fire gases being forced out through openings
  • Pulsation of fire gases through openings
  • Deflagration through the opening
24
Q

Fire science

Define the term “Backdraught”?

A

The explosive or rapid burning of heated gases that occurs when oxygen is introduced into a building or compartment that has not been properly ventilated and has a depleted supply of oxygen due to fire

25
Q

Fire Science

What are the common internal signs of a possible backdraught?

A

Low neutral plane No visible flame

26
Q

Fire Science

What actions should be taken when dealing with a backdraught?

A
  • Stay low Cover door with charged hose
  • Spray gases exiting openings
  • Only open doors when crews insitu
  • Pulse spray
  • Consider high level opening with covering jet
27
Q

Fire Science

What conditions are needed for a back draught to occur?

A

A compartment that has sufficient heat & fuel but is poorly ventilated

28
Q

Fire science

What conditions are needed for a back draught to occur?

A

A compartment that has sufficient heat & fuel but is poorly ventilated

29
Q

Fire science

What are the signs of back draught ?

A
  • fire with limited or no ventilation.
  • thick black, yellow or cold smoke.
  • small blue flames around doors and windows.
  • hot doors and windows.
  • soot blackened windows.
  • lack of visible flame within the compartment.
  • air drawn in (whistling noise).
  • smoke pulsating through small gaps in openings
30
Q

Fire science

What are the internal signs of backdraught ?

A
  • low neutral plane
  • darkening of fire gases
  • inrush of air & fire gases being forced out through openings
  • pulsation of fire gases through openings
  • deflagration through the opening
31
Q

Fire Science

What are passive agents?

A 
Passive agents (passives) exist alongside the triangle of combustion in the combustion process.
 They are present in any combustion process and take no part in the chemical reaction. But they do affect a fire’s behaviour by absorbing or stealing some of the heat that makes up part of the triangle
32
Q

Fire Science

What are the LEL & UEL for Acetylene gas?

A

Between 2.5% & 100%

33
Q

Fire Science

What are they LEL & UEL for Propane gas?

A

2.1% & 9.5%

34
Q

Fire Science

Give some examples of passive agents?

A
  • Non-flammable gases: carbon dioxide, water vapour.
  • Soot: carbon particles
  • Weather: temperature and humidity
  • Nitrogen: a constituent of air that remains inert throughout combustion
  • Compartment boundaries: walls and ceilings.
35
Q

Fire science

What are the common internal signs of a possible backdraught?

A

low neutral plane

no visible flame

36
Q

Fire science

What is the expansion Ratio When water turns to steam ?

A

The ratio is1700:1 @100oC, although this ratio increases signifcantly as the temperature increases

37
Q

Fire Science

Define the term ‘Fire Gas Explosion’?

A

Ignition of fire gases that have accumulated outside the original fire compartment

38
Q

Fire Science

What effect does cooling fire gases have on compartment involved fires?

A
  • Creates a safer approach for Ff’s
  • Helps prevent Flashovers
  • Helps prevent Backdraughts
39
Q

Fire science

Define the term ‘Fire Gas Explosion’?

A

Ignition of fire gases that have accumulated outside the original fire compartment

40
Q

Fire Science

What would a yellow flame indicate ?

A

That a flame is fuel rich

41
Q

Fire Science

What are the three main headings when describing methods of extinguishing fires?

A
  • Direct
  • Indirect
  • Gas cooling
42
Q

Fire science

What effect does cooling fire gases have on compartment involved fires?

A
  • creates a safer approach for firefighters
  • helps prevent flashovers
  • helps prevent backdraughts
43
Q

Fire science

What are the three main headings when describing methods of extinguishing fires?

A
  • direct
  • indirect
  • gas cooling
44
Q

Fire science

What would a yellow flame indicate ?

A

That a flame is fuel rich

45
Q

Fire science

What are passive agents?

A 
Passive agents (passives) exist alongside the triangle of combustion in the combustion process.
 They are present in any combustion process and take no part in the chemical reaction. But they do affect a fire’s behaviour by absorbing or stealing some of the heat that makes up part of the triangle
46
Q

Fire science

What are the LEL & UEL for acetylene gas?

A

between 2.5% & 81%

47
Q

Fire science

What are they LEL & UEL for propane gas?

A

2.1% & 11.1%

48
Q

Fire science

Give some examples of passive agents?

A
  • non-flammable gases: carbon dioxide, water vapour.
  • soot: carbon particles
  • weather: temperature and humidity
  • nitrogen: a constituent of air that remains inert throughout combustion
  • compartment boundaries: walls and ceilings.

Fire science, flashovers & backdraughts (2 decks)

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