Fire Science 2

Question 1

What are the two types of flame?

Answer 1

Diffused

Pre-mixed

Question 2

What are the signs of a diffused flame?

Answer 2

Slow, bright, lazy. flickering.

Orange/red in colour

Question 3

Candles are only _____ efficient, releasing ______ into a room

Answer 3

Candles are only 25% efficient, releasing unburnt fuel into a room

Question 4

What type of flame will a burning sofa produce?

Answer 4

A diffused flame

Question 5

What are the characteristics of a pre-mixed flame?

Answer 5

More Violent, blue in colour, cleaner burn, noisier.

Question 6

What is the difference between a diffused and a pre-mixed flame?

Answer 6

A pre-mixed flame has air mixed with flammable gasses before combustion. This results in a more efficient combustion.

Question 7

What is the stoichiometric ratio?

Answer 7

The optimum air to fuel ratio for combustion to occur.

Question 8

What is the upper explosive limit?

Answer 8

The highest possible concentration of a fuel in a mixture for it to ignite.

If the mixture is above the UEL, it is described as too rich to burn.

Question 9

What is the lower explosive limit?

Answer 9

The lowest possible of a concentration of a fuel in a mixture for it to ignite.

If the mixture is below the LEL, it is described as to lean to burn.

Question 10

What is the ideal mixture?

Answer 10

Every gas has a particular concentration at which the amount of gas and the amount of oxygen is exactly right for combustion to occur.
At this point, combustion will have the maximum force.

Question 11

Why is acetylene such a dangerous gas when released into the atmosphere?

Answer 11

Due to its wide range of flammability.

Question 12

What is a flashover?

Answer 12

The sudden and sustained transition from a fire in a room to a room on fire.

Question 13

What are the four stages of fire development?

Answer 13

Developing.
Flashover.
Fully developed.
Decay.

Question 14

What will cause a fire to decay?

Answer 14

A reduction of the fuel, heat or oxygen available to the fire.

Question 15

What is the over-pressure?

Answer 15

A mixture of hot fire gasses which have risen from the seat of the fire to the top of the compartment, creating a cloud with a higher than atmospheric pressure.

Question 16

What is the neutral plane?

Answer 16

The visible divide between the over-pressure and under-pressure.

Question 17

What is the under-pressure?

Answer 17

The area at the bottom of the compartment at less than atmospheric pressure, caused by air being drawn towards the fire.

Question 18

What three factors affect fire progression?

Answer 18

Insufficient fuel
Smouldering fire.
An airtight compartment.

Question 19

How will an airtight compartment affect a fire?

Answer 19

The fire will consume all of the oxygen in the room, causing it to decay.
The heat in the room will cause items to continue to pyrolyse and smoulder.

Question 20

A higher ceiling will slow a fire’s development.

True or false.

Answer 20

True

Question 21

A fire in the centre of the room will develop ___ times faster than a fire in the centre of a room.

Answer 21

4 times faster.

Question 22

If a fire is in the corner of a compartment, the flame height will _______ in height for every _______ of fire development, until the ceiling is reached.

Answer 22

The flame height will DOUBLE in height for every MINUTE of fire development.

Question 23

What are the signs of a flashover? (List of 8)

Answer 23

A ventilated fire with an oxygen supply.
Visible flames at ceiling height.
The production of fire gasses.
High temperatures and an increasing rate of combustion.
Neutral plane lowering.
Sudden increase in fire development.
Pyrolysis at floor level.
Turbulence in the neutral plane.

Question 24

What actions should be taken if flashover occurs?

Answer 24

Firefight from outside the compartment.
Communicate to the ECO/IC
Ventilate to remove fire gasses.
Use the TIC to assess the temperature of the over-pressure.
Pulse the over-pressure to cool it.

Question 25

What is a backdraught?

Answer 25

Sudden deflagration, caused by air being introduced to an oxygen starved compartment where there is a build up of fire gasses.

Question 26

List 4 signs of a potential backdraught.

Answer 26

A poorly ventilated fire which has been burning for some time.
Fire gasses being pushed through gaps under pressure.
Blackened windows with no signs of flame.
Low neutral plane.

Question 27

After informing the ECO/IC, what must firefighters do if a backdraught has been indicated?

Answer 27

Ventilate prior to entry (on the orders of the IC)
Use TIC to assess the temperatures inside the compartment.
Use door procedure.
Pulse spray to cool and dilute fire gasses.

Question 28

Define fire gas ignition

Answer 28

A sudden ignition of fire gasses that have accumulated outside of a compartment.

Question 29

Name three causes of fire gas ignition

Answer 29

Pyrolysis of material in an adjacent compartment.

Ignited fire gasses leaked from the fire compartment.

The construction of the building causing smouldering of material (e.g. sandwich panels).

Question 30

What actions should be taken if fire gas ignition is indicated? (list of 4)

Answer 30

Communicate to the ECO/IC.
Consider withdrawal.
Ventilate to remove the gasses (on the command of the IC)
Cool and dilute the gasses using pulse spraying.

Question 31

What element of a fire triangle is lacking if a backdraught is developing?

Answer 31

Oxygen