DATE: 2009-09-04 INSTRUCTOR: Bob Kissner
SUBJECT: Fire Behaviour
LEARNING OUTCOMES
TOTAL TIME: 3 hours.
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Upon completion of this lesson, the learner will be able to:
1. Define the terms “combustion” and “spontaneous combustion”.
2. List the elements of the fire triangle and the fire tetrahedron and
their relationship to one another.
3. Describe the effects of heat on solid, liquid and gaseous fuels.
4. Define the following terms:

Flash point.

Fire point.

Auto ignition temperature.

Flashover.

Backdraft.

Rollover.

Pyrolysis.

B.L.E.V.E.

Specific Gravity.

Vapour Density.

Upper Explosive Limit/Lower Explosive Limit.
5. Define and describe the stages of fire growth.
6. Define and describe the four methods of heat transfer.
7. Describe the products of combustion.
8. Identify the four classes of fire give two examples of fuels in each
class.
9. Describe common fire extinguishing agents.
10. Describe the extinguishing agents appropriate to each class of
fire along with the advantages/disadvantages of each.
11 . Describe the four attributes of “reading smoke” and their
application in determining fire stage and growth.
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INTRODUCTION
Every topic covered in the Pre Service Fire Program can be hinged on the firefighter’s knowledge of fire behaviour and chemistry. A thorough knowledge of this material will, in fact, be a necessary tool to ensure firefighter life safety. (Describe the concept of a fire burning in a structure to that of a fire in a box). If we do not know what is happening in the box and how the box will be affected, we are at risk of being in danger due to the fire or the collapse of the box.
Describe the changes that have affected firefighting in the past several decades:
 The “box” is often made of lightweight construction.
 The “box” is often filled with materials which produce much greater amounts of energy than in the past (p. 103 of 5 th ed.)
 We are sending firefighters into the “box” in a completely protective covering (making it more difficult to discern changing conditions).

We have seen a decrease in the number of structure fires.
(Show backdraft video clip from 5 th edition DVD).
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PRESENTATION:
Lesson Outline:
1. Introduce the concept of the fire triangle.

Oxygen, heat and fuel.

Fuel: i. Matter-anything that takes up space. ii. Composed of atoms/molecules. iii. Known as the reducing agent which combines with oxygen.

Oxygen: i. Elemental gas. ii. Consists of 2 atom molecule. iii. Chemical formula 02.
BBD or Flip Ch.
PPT 3-10
PPT 3-27
PPT 3-36 to 3-39

iv. Oxidizing agent which combines with reducing agent. v. May be substance other than just oxygen. vi. Air is normally 21% oxygen. vii. Combustion is not supported below 14% but this amount can be lowered by high temps. viii. O2 rich atmospheres can cause normally non

Heat: combustibles to burn. i. Form of energy. ii. Describe difference between heat and temperature. iii. Describe the forms of heat energy and sources of each:
1. Chemical
2. Electrical
3. Mechanical
4. Nuclear
5. Solar iv. Describe spontaneous heating or combustion-chemical and biological (see textbook). v. Describe methods of heat transfer:
1. Conduction.
2. Convection.
3. Radiation
2. Explain the effects of heat on matter:

Solids: i. Atoms cannot move vertically or horizontally-constant shape and volume. ii. Heat causes vibration which will result in expansion and contraction. p. 104 of 5 th ed.
Table 3-7
PPT 3-12 to 3-19 p. 91-93 of 5 th ed.
PPT 3-20 to 3-25 p. 94-95 of 5 th ed.
BBD or Flip ch. p. 90 of 5 th ed. p. 98 of 5 th ed.


Liquids: i. Continued heating of solids will cause them to turn to liquidsmolecules slide around and across each other. ii. Known as fusion or melting.
iii. Constant volume but takes shape of container. iv. Define the following terms related to liquids:
1. specific gravity.
2. flash point.
3. fire point.
4. auto ignition point.
5. See Table 3.4 on p. 99 of
5 th edition.

Gases: i. Continued heating causes molecules to lose ordinary arrangement. ii. Take shape and volume of container. iii. Define the following terms related to gases:
1. Vapour density.
2. Upper and lower explosive limits and flammable range. iv. Define B.L.E.V.E. (p. 774 of 5 th ed.) and show sample video.

Use a chart on the BBD to outline fusion, vapourization, condensation, sublimation, freezing. Explain that the change of a solid to a gas in fire situations is know as “pyrolysis”.
 Describe the production of “free radicals”: i. Additional heating causes a chemical change rather than a p. 98 of 5 th ed. p. 98 of 5 th ed. p. 105 of 5 th ed.
OAFC Bleve video.
BBD or Flip ch. p. 90 of 5 th ed.
PPT 3-11
BBD or Flip ch. p. 114 of 5 th ed.
BBD or Flip ch.

physical one . Molecules actually break down and combine with other molecules
(oxygen being one of the most abundant) to make new compounds-byproduct of this process is the production of heat which now causes a chain reaction to occur. The process has now become exothermic
(producing its own heat) rather than endothermic (requiring an external source of heat).

Explain the need for a fourth sidechemical chain reaction.
3. Define “combustion”: An exothermic chemical reaction that is a self sustaining process of rapid oxidation of a fuel that produces heat and light. Discuss speed at which oxidation reactions can occur:

Slow-rusting.

Rapid-combustion.

Instantaneous-explosion (eg. sawdust or grain).
4. Describe stages of fire development:

Incipient: i. 4 sides of tet come together and fire ignites-can be piloted or unpiloted. ii. Fire is small and confined. iii. Plume of hot gases and flame reaches ceiling and starts mushroom horizontally. iv. Space is habitable at this stage. v. See Table 3.10 on p. 114 of 5 th ed.
PPT 3-55 to 3-70
Show sample videos.


Growth: i. Fire is now influencing the environment in the compartment. ii. Plume of air in entrained into the room and thermal layering begins to occur. iii. Smoke begins to exit from upper area of openings and air enters the lower area. iv. This stage ends with:
1. isolated flames.
2. rollover.
3. flashover: a. describe signs of impending flashover (p.119 of
5 th ed.) b. describe procedures to follow if indicators

Fully Developed: are observed. i. Stage when energy released is at its maximum and is limited only by fuel or oxygen. ii. Fire is vent controlled in that energy released depends on size and number of compartment openings.

Decay Stage: i. Fuels or oxygen will not support flaming combustion. ii. If the fire is fuel controlled and not vent controlled, the heat release rate will drop but products of combustion can still accumulate in the hot
Show sample videos. p. 109 of 5 th ed.
PPT 3-44 to 3-45
Dodson DVD.
Sample Videos.

compartment and ignite-a smoke explosion. iii. If fire is vent controlled, the lack of oxygen will not support flaming combustion. The amount of heat will still enable flammable products of combustion to be produced.
The introduction of oxygen at this stage results in a backdraft. Describe the signs of potential backdraft:
1. pressurized smoke exiting small openings.
2. black smoke becoming gray-yellow.
3. confinement with high heat.
4. little or no flame.
5. puffing (breathing smoke).
6. high smoke volume.
7. smoke stained windows.
5. Outline the various products of combustion-have class “brainstorm” what a fire produces. Include the following in particular.

Particulates will be covered with condensed toxins as gases cool.

The dangers of carbon monoxide.

The chart on p. 109 of 5 th ed.
6. Explain the concept of “reading smoke”

Smoke is a fuel. It is not burning because it is not hot enough or there is not enough oxygen.

Smoke is an indicator of what the fire is doing and what it may do. p. 130-132 of 5 th ed.
BBD or Flip Ch.
PPT 3-70 to 3-84
BBD or Flip Ch.
PPT 3-48 to 3-54


Smoke reading can be affected by outside temperature, size of the box, material which is burning.

Rate of change is a very important factor to consider.

The four attributes of smoke reading; i. Density: Describes quality of burning. Dense smoke indicates an oxygen deficient fire or a fire nearing ignition temperature. ii. Colour: May indicate material which is burning. White is early stage but may indicate a serious fire in a large structure
(become white as it travels long distances). Brown may indicate structure itself is involved (review dangers of lightweight construction).
Black may indicate late stage fire or involvement of hydrocarbons. iii. Volume: May indicate amount of material burning but is affected by the size of the container. iv. Velocity: A measure of how hot the smoke is. Discuss concept of black fire-dense smoke with high velocity which indicates it is near ignition temperature.
 Show the Dodson DVD “The Art of
Reading Smoke”. Then show other video samples.
7. Discuss the methods of extinguishment using pages 130-132 of the 5 th edition.

Temperature reduction:
KFD power point
CD on Building
Construction.

i. Water. ii. Foam.

Fuel Removal: i. Foam. ii. Shutting of a gas valve. iii. Dry chemicals.

Oxygen Exclusion: i. CO2. ii. Foam. iii. Lid on a pan. iv. Dry powder (Class D)

Chemical Flame Inhibition: i. Dry chemical. ii. Dry powder.
8. Use a chart to describe the classes of fire, giving and example of each and examples of suitable extinguishing agents.

A-normal combustibles (wood, paper) extinguished by water, foam, multi-purpose dry chemical.

B-flammable liquids (gasoline, oil, diesel) extinguished by CO2, dry chemical or foam.

C-energized electrical equipment extinguished by CO2, dry chemical or (once de-energized) by water.

D-combustible metals (magnesium, aluminum) extinguished by dry powder specific to the metal.

K-combustible cooking oils and greases extinguished by a Class K extinguishing agent.
SUMMARY
We have defined fire scientifically, discussed the products produced when a fire occurs, explained the stages a fire goes through, classified fire into groups, described the various extinguishing agents

that are available, learned the importance of reading smoke and building construction in order to remain safe and looked at how we can make buildings safer. It is hoped that this lesson will enable you to better understand what is actually occurring when a fire takes place in order to be as safe as possible.
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APPLICATION AND TEST
1. Define the term “combustion”.
2. What are the four sides of the fire tetrahedron.
3. Define the following terms;

Flash point.

Fire point.

Lower explosive limit.

B.L.E.V.E.

Flashover.

Backdraft.
4. Name and describe the stages of fire growth in a compartment.
5. What is convection?
6. Describe one toxic product of combustion and explain its hazards.
7. Describe and name an extinguishing agent for each of the classes of fire.
8. Name the four attributes used to read smoke and describe what each indicates.
ASSIGNMENT
This topic can be related to all of the other topics in this course. Keep in mind the concepts that have been covered in order to better understand the additional material you will be presented with.
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TRAINING AIDS: REFERENCES:
Essentials of Firefighting 5 th ed. Overhead projector.
Ontario Standardized Curriculum Computer and LCD.

for Firefighters-Module 2. Blackboard or flipchart.
Essentials of Firefighting 5 th
Ed. CD
Essentials of Firefighting 5 th
Ed. Power Point Ch. 3
KFD sample videos for
Flashover/backdraft.
OAFC B.L.E.V.E. video.
Dodson “The Art of Reading
Smoke” DVD.
KFD building construction
Power point.