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Questions and Answers
What is necessary for a substance to oxidize?
What is necessary for a substance to oxidize?
What must be reached for a vapor to start burning?
What must be reached for a vapor to start burning?
What are the three elements of the fire triangle?
What are the three elements of the fire triangle?
What is the key difference between the fire triangle and the fire tetrahedron?
What is the key difference between the fire triangle and the fire tetrahedron?
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How are vapor molecules different from solid or liquid molecules?
How are vapor molecules different from solid or liquid molecules?
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What is a necessary condition for fire to occur?
What is a necessary condition for fire to occur?
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What are the three elements required for combustion?
What are the three elements required for combustion?
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Which class of fire involves flammable liquids?
Which class of fire involves flammable liquids?
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What is the oxygen percentage needed to support flaming combustion?
What is the oxygen percentage needed to support flaming combustion?
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Which type of fire involves electrical equipment?
Which type of fire involves electrical equipment?
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What kind of fire involves ordinary combustibles like wood and paper?
What kind of fire involves ordinary combustibles like wood and paper?
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Which class of fire is associated with cooking oil or fat fires?
Which class of fire is associated with cooking oil or fat fires?
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Study Notes
Oxidation
- For a substance to oxidize, it must lose electrons to another substance. This is a chemical reaction involving the transfer of electrons.
Vapor Ignition
- For a vapor to ignite and burn, it must reach its ignition temperature and be present in sufficient concentration within a combustible range in the air.
Fire Triangle
- The three elements of the fire triangle are: heat, fuel, and an oxidizer (typically oxygen).
Fire Triangle vs. Fire Tetrahedron
- The key difference is that the fire tetrahedron adds a fourth element: a chain reaction. The chain reaction describes the continuous cycle of chemical reactions that sustains combustion. The fire triangle only shows the prerequisite conditions.
Molecular States and Combustion
- Vapor molecules, unlike solid or liquid molecules, possess higher kinetic energy and are more readily dispersed, increasing the chances of mixing with the oxidiser for combustion to occur. This dispersion is critical for the spread and intensity of fire.
Condition for Fire
- A necessary condition for fire is the presence of all three elements of the fire triangle (heat, fuel, oxidizer) in the correct proportions simultaneously—which allows for the chain reaction enabling sustained combustion.
Combustion Requirements
- The three elements required for combustion are fuel, oxidant (usually oxygen), and heat.
Fire Classes
- Class B fires involve flammable liquids (e.g., gasoline, oil).
Oxygen for Flaming Combustion
- An oxygen percentage of approximately 16% is needed to sustain flaming combustion. Lower levels may support smoldering combustion.
Electrical Fires
- Class C fires involve energized electrical equipment.
Ordinary Combustible Fires
- Class A fires involve ordinary combustibles such as wood, paper, cloth, and trash.
Cooking Oil/Fat Fires
- Class K fires involve cooking oils and fats.
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Description
This quiz covers the theory of fire, including the start of a fire and the important concept that only vapors can burn. It also discusses the three states of matter and the relationship between molecules and oxygen in the process of oxidation.
