2.5.8Chemical Bonding, Application Of Chemical Reactions and Organic Chemistry
The Fire Triangle
5 min read 7 parts Lesson 48 of 54 Unit quiz
Section 1 of 7The three sides of the triangle
Fire
Fuel
- Fuel Something that can burn, such as wood, paper, petrol or gas.
Heat
- Heat Enough energy to raise the fuel to its ignition temperature so combustion can start and carry on.
Oxygen
- Oxygen Combustion is a reaction with oxygen, which air supplies (about 21%).
The key idea
- The key idea All three must be present together.
- Take away any one and the fire goes out, and a fire cannot start unless all three meet.
Section 2 of 7Removing the fuel
Fire-resistant materials
- Fire-resistant materials Clothing, furniture and building materials can be treated so they do not ignite easily.
Compartments
- Compartments Modern buildings have fire-proof sections in walls and ceilings and internal fire doors,
- so a fire cannot reach new fuel in the next room.
Fire breaks
- Fire breaks In forests and moorland a strip of land is cleared of all plants.
- The fire reaches the gap, has no fuel and stops spreading.
Section 3 of 7Removing the heat
1Spray water
- Spray water Large amounts of water absorb energy from the burning material.
2Temperature falls
- Temperature falls When the fuel drops below its ignition temperature, combustion cannot continue.
3Fire is out
- Fire is out Water must not be used on electrical fires,
- because it conducts electricity and may cause electric shocks,
- or on oil fires,
- because it breaks the oil into droplets that increase the surface area and make the fire burn more fiercely.
Section 4 of 7Removing the oxygen
1
Smother the fire with a fire blanket, which stops air reaching the fuel.
2
Use a carbon dioxide or foam extinguisher; these cover the fuel with a layer that keeps oxygen away.
3
Keep doors closed in a burning building so that the fire is held in a space with limited oxygen and burns out.
4
Never open a door to a fire for no reason, because it lets in fresh oxygen and the fire grows quickly.
Section 5 of 7Choosing the method
| Fire type | Suitable method | Reason |
|---|---|---|
| Wood or paper | Water | Cools the fuel below its ignition temperature |
| Electrical | Carbon dioxide extinguisher | Removes oxygen without conducting electricity |
| Cooking oil | Fire blanket or foam | Cuts off oxygen; water would spread the fire |
| Moorland | Fire break | Removes fuel ahead of the flames |
Section 6 of 7Key terms
| Term | Meaning |
|---|---|
| Fire triangle | A model showing that a fire needs fuel, heat and oxygen. |
| Ignition temperature | The lowest temperature at which a fuel starts to burn. |
| Fire break | A strip of land cleared of fuel to stop a fire spreading. |
| Extinguisher | A device that puts out a fire by cooling it or cutting off oxygen. |
| Compartment | A section of a building designed to hold back a fire. |
Section 7 of 7Exam technique
1
Saying water suits every fire. It is dangerous on electrical and oil fires.
2
Forgetting that heat is a side of the triangle and describing a fire as needing only fuel and oxygen.
3
Writing that fire blankets remove the heat. They work by excluding oxygen.
4
Opening a door to check on a fire. This supplies fresh oxygen and makes the fire spread faster.