Fire Science 2

Question 1

What are the two main types of flame?

Answer 1

Diffused
Slow and bright, flickers to seek oxygen, unclean burn, orange/red

Premix
Hotter, clean burn, gases are mixed prior to ignition, blue flame

Question 2

What does LEL and UEL stand for, and what are their definitions?

Answer 2

Lowe Explosive Limit
The lowest concentration of a fuel that will support a self-propagating flame

Upper Explosive Limit
The highest concentration of a fuel that will support a self-propagating flame

Question 3

What are the four phases of Fire development?

Answer 3

Phase 1 - Developing
Fire develops at a slow rate, but the rate increase in time, due to passives reaching their thermal load and reflecting heat back into the room.

Phase 2 - Flashover
Sharp rise in temperature causing pyrolysis

Phase 3 - Fully Developed
Fuel or oxygen in the compartment will affect how long the compartment and all it’s contents will burn

Phase 4 - Decay
The fire will gradually die back as fuel or oxygen is consumed

Question 4

What does thermal load mean?

Answer 4

When passives reach their thermal load, it means they can no longer absorb heat from the fire, so they release heat back into the room, causing a rapid increase in temperature

Question 5

What are the two areas of pressure called in a fire compartment, and what divides them?

Answer 5

Over Pressure - Pressurised above atmospheric pressure

Under Pressure - Slightly below atmospheric pressure

The Neutral Plan is the visible border between the two.

Question 6

What is the 4-2-1 rule of thumb?

Answer 6

A Flashover occurs rapidly in a fire in the corner of a room (4),
Twice as quickly as against one wall (2), and four times quicker than a fire in the middle of a room compartment (1)

Question 7

What are the three main fire hazards that firefighters might occur during a fire?

Answer 7

Flashover
Backdraught
Fire Gas Ignition (explosion)

Question 8

What is a Flashover?

Answer 8

A sudden and sustained transition of a ground fire into a fully developed fire.
A fire in a room to A room on fire

Question 9

What temperatures can be reached in the over pressure?

Answer 9

700 - 1000 •c

Question 10

What are the signs of a Flashover?

Seven answers

Answer 10

1- A ventilated Fire with an adequate oxygen supply
2- Flames visible in the fire gases at ceiling level
3- High temperatures and an increase rate of combustion
4- Neutral Plane moving down
5- Sudden increase in fire development
6- Pyrolysis at floor level in the compartment
7- Increase turbulence of neural plane

Question 11

If the signs of a Flashover are identified, what actions should be considered?
Six answers

Answer 11

1- Withdrawing and firefighting from outside of the compartment
2- Communicate the hazard to other firefighters, the ECO,sector commander or IC
3- Ventilated to remove gases, only with IC permission
4- Use Thermal image camera to assess temperatures
5- Teams should stay low in cooler air
6- Pulse spray into the over pressure to cool gases and reduce radiated heat

Question 12

What is the definition of a Backdraught?

Answer 12

A deflagration caused by air being introduced to a fire compartment that is oxygen starved

Question 13

What is the definition of deflagration?

Answer 13

An intense fire that moves rapidly outwards in all directions through flammable gas

Question 14

What are the external signs of a backdraught?

Five answers

Answer 14

1- Fire with limited or no ventilation
2- Fire has been burning for some time
3- Fire gases being push out under pressure from gaps
4- Windows blackened with no visible signs of flame
5- Fire gases pulsing out from gaps

Question 15

What are the internal signs of a backdraught?

Five answers

Answer 15

1- Low Neutral Plane
2- Darkening of fire gases
3- In-rush of air and fire gases forced out through the opening
4- Pulsating of gases through an opening
5- Deflagration through an opening

Question 16

If the signs of Backdraught are identified, what actions should be considered?
Five answers

Answer 16

1- Communicate the hazard with other firefighters, the ECO, sector commander or IC
2- Consider ventilating the compartment prior to entry
3- Use the TIC to access temperatures
4- Always Use correct door procedures when making an opening
5- Pulse spray the interior to dilute the fire gases

Question 17

What is Fire Ignition?

Answer 17

A sudden deflagration or explosion caused by the ignition of fire gases accumulated outside the fire compartment

Question 18

If the signs of fire gas ignition are identified, what actions should be considered?
Four answers

Answer 18

1- Communicate the hazard to other firefighters and ECO, sector commander or IC
2- Consider withdrawing form the building
3- Ventilate the fire gases from the adjacent compartments
4- Cool and dilute fire gases that leaked from the fire compartment

Question 19

What happens to gases when pulsing takes place within a fire compartment?

Answer 19

The oxygen exhausts, flames go down
Temperature drops, lowering the pressure
This draws air into the compartment through any gaps
This allows burning to take place, increasing temperature, pressure increasing preventing future air from entering

Question 20

What are the signs of Fire gas ignition?

Two answers

Answer 20

1- Fire has been burning for some time

2- Accumulation of fire gases outside the fire compartment