Fire and Its Stages

Definition and Composition

• Fire is the rapid oxidation of a fuel source, resulting in the release of heat, light, and various products of combustion.
• Fire is a chemical reaction that involves the combination of fuel, oxygen, and heat.

Stages of Fire

1. Incipient stage: The initial stage of fire, characterized by smoldering and a small amount of smoke.
2. Growth stage: The stage where the fire spreads and grows, fueled by more oxygen and combustible materials.
3. Fully developed stage: The peak stage of fire, characterized by intense heat, flames, and a large amount of smoke.
4. Decay stage: The final stage of fire, where the fuel is depleted, and the fire dies out.

Fire Triangle

• The three essential elements required for a fire to start and sustain:
  • Fuel: The material that undergoes combustion (e.g., wood, gasoline, propane).
  • Oxygen: The oxidizer that supports combustion (typically atmospheric oxygen).
  • Heat: The energy source that ignites the fuel (e.g., flame, spark, hot surface).

Fire Types

• Class A: Fires involving ordinary combustible materials (e.g., paper, wood, cloth).
• Class B: Fires involving flammable liquids or gases (e.g., gasoline, propane, oil).
• Class C: Fires involving electrical equipment (e.g., appliances, wiring, circuit breakers).
• Class D: Fires involving combustible metals (e.g., magnesium, titanium).

Fire Hazards and Risks

• Flashover: A sudden and intense increase in fire temperature, often causing a room to become fully engulfed in flames.
• Backdraft: A sudden explosion of flames that occurs when oxygen is reintroduced to a fire that has depleted its oxygen supply.
• Fire spread: The movement of fire from one location to another, often through convection or radiation.

Definition and Composition

• Fire is a rapid oxidation process of a fuel source releasing heat, light, and combustion products.
• Combustion requires three elements: fuel, oxygen, and heat.

Stages of Fire

• Incipient Stage: Initial phase with smoldering and minimal smoke.
• Growth Stage: Fire expands, fueled by increased oxygen and available combustibles.
• Fully Developed Stage: Peak intensity with high heat, flames, and significant smoke.
• Decay Stage: Final phase where fire diminishes due to fuel depletion.

Fire Triangle

• Essential components for fire ignition and maintenance:
  • Fuel: Combustible materials like wood, gasoline, or propane.
  • Oxygen: Typically from the atmosphere, supporting combustion.
  • Heat: Energy source igniting the fuel, via flame, spark, or hot surface.

Fire Types

• Class A: Ordinary combustibles, including paper, wood, and cloth.
• Class B: Flammable liquids or gases such as gasoline and oil.
• Class C: Fires involving electrical equipment, like appliances and wiring.
• Class D: Fires that involve combustible metals, e.g., magnesium and titanium.

Fire Hazards and Risks

• Flashover: Rapid temperature rise causing a space to ignite fully.
• Backdraft: Explosive re-ignition of a fire when fresh oxygen is introduced.
• Fire Spread: Movement of fire facilitated by convection or radiation to other areas.