Structural Firefighting - Elements

Question 1

What are the four stages of a compartment fire?

Answer 1

1. Developing stage
2. Flashover stage
3. Fully developed stage
4. Decay stage

Question 2

What are the two key signs used to determine likely fire behavior?

Answer 2

1. Height
2. Turbulence

Question 3

What are the signs of a flashover?

Answer 3

• Ventilated fire (an open door is sufficient)
• Painful radiant heat with crews forced low by high temperatures
• Lowering of the neutral plane with flames at ceiling height (‘fingers of flame’ in the smoke)
• Hot surfaces
• Increased rate of pyrolysis
• Increased turbulence of the neutral plane
• Flaming occurs throughout the volume of the compartment
• A ‘billowing effect’ from the gases may be seen

Question 4

What is a backdraught?

Answer 4

The sudden introduction of air into a severely under ventilated fire resulting in an explosive like event.

Question 5

What are the signs of a backdraught?

Answer 5

• Fire with limited or no ventilation
• Lack of visible flames
• Thick roiling black, yellow and white smoke
• Dirty brown smoke
• Smoke pulsating through small gaps & openings
• Air being drawn in (whistling noise)
• Blackened deposits on windows

Question 6

What are the 3 extreme fire bahaviours?

Answer 6

1. Flashover
2. Backdraught
3. Fire Gas Ignition

Question 7

What is Fire Gas Ignition?

Answer 7

Flammable fire gases from one compartment can enter an adjacent compartment through convection process.

The addition of air is not always a requirement for ignition of these gases, which have already formed into an ideal pre-mixed state, simply awaiting an ignition source.

Question 8

What 3 elements will contribute to Fire Gas Ignition?

Answer 8

1. Conduction: heat can be conducted from the fire compartment to other compartments.
2. Leakage: there can be leakage of fire gases from the compartment that is on fire through various voids, cavities, and ducting to other compartments.
3. Construction: the construction of the premise will influence the possibility of a fire gas explosion.

Question 9

What are the 3 things water does as an extinguishing agent?

Answer 9

1. Reduces fuel
2. Reduces heat
3. Reduces oxygen

Question 10

What is the expansion rate of water to steam?

Answer 10

• 1:1700 at 100°Celcius.
• 1:3500 at 450°Celcius.

Question 11

What hose line would you use for a small residential fire?

Answer 11

38mm

Question 12

Define pyrolysis.

Answer 12

Decomposition of a substance through the application of heat.

Question 13

Define flashover.

Answer 13

The sudden and sustained transition from a developing fire to a fully developed fire.

Question 14

Describe indirect extinguishment.

Answer 14

Applying water spray onto super-heated surfaces and/or overhead gases in a compartment, to create a mass of steam that displaces the oxygen to smother the fire.

Question 15

Describe direct extinguishment.

Answer 15

The extinguishment agent is applied directly onto the burning fuel, using a jet or spray.

Question 16

What are the effects of direct extinguishment?

Answer 16

• Cools the surface below the temperature at which combustion can occur.
• Can be used to stop pyrolysis.
• Care must be taken to avoid excessive water damage.
• Care should be taken not to disturb embers which can be ignition sources.
• Can draw/entrain air into the fire compartment.

Question 17

What are the effects of indirect extinguishment?

Answer 17

• Cools and dilutes the fire gases
• Cools burning combustibles and structure of the compartment
• Large quantities of steam produced have a smothering effect on the fire
• Lowers neutral plane, reducing vision. Steam can have a debilitating effect on firefighters and any victims.
• Should be applied from outside of the compartment or from a distance.

Question 18

Describe gas cooling.

Answer 18

A hose stream technique used to cool hot fire gases below their auto-ignition temperatures, preventing further fire spread and the potential for flashover.

To employ gas cooling, direct a water spray into the overhead hot gases to cool and dilute them, thereby reducing the potential to ignite.