Fire Chemistry Basics

Fire Chemistry

• Fire is a chemical reaction caused by fuel, oxygen, and heat.

• Combustion is the continuing reaction of a fire.

• Ignition is the initial stage of fire.

• The fire triangle represents the three components necessary for maintaining a fire

  • Fuel (solid, liquid or gas)
  • Oxygen (to sustain combustion)
  • Heat (applied heat to ignite)

• Removing one component from the fire triangle will extinguish the fire.

  • Example: Removing the fuel by taking away a flammable substance, or cooling the heat to stop the reaction.

• Different types of fuels have different characteristics.

  • Flashpoint: The temperature where a substance releases enough vapor to ignite.
  • Fire point: The temperature where sustained combustion can occur

• Flammable liquids have a flash point below 38°C and are more hazardous than combustible liquids which have flash points between 38°C - 94°C.

• Combustion of solid fuels occurs when heat is applied to a solid, releasing flammable vapors that ignite and burn.

• Combustion of liquid fuels releases vapor that burns, but the liquid itself does not burn.

• Common ignition sources include open flames, mechanical action, and electrical sources.

• Classes of fire:

  • Class A: Ordinary combustible solids (wood, textiles, etc)
  • Class B: Flammable or combustible liquids (oil, paints, etc).
  • Class C: Flammable gases
  • Class D: Combustible metals
  • Class F: Cooking mediums (vegetable or animal fats)

• Common methods to extinguish a fire include removing the fuel, cooling the material, and excluding oxygen.

Products of Combustion

• Combustion produces thermal and non-thermal products.
• Thermal products include heat and flame
• Non-thermal products include smoke and gases.
• Some combustion gases can be corrosive or harmful if mixed with water.
• Heat from a fire can cause considerable damage to property, including the potential collapse of steel structures.

Types of Explosions

• Explosions are rapid, violent oxidation reactions that produce heat, smoke, light, and overpressure.
• Physical explosions occur due to physical forces
• Chemical explosions occur due to rapid chemical reactions.
• Explosions are often classified based on the presence of flammable gases and vapors, dusts, and other flammable materials.
• Hazardous areas (like Zones) are classified by proximity to flammable substances.
• Preventing explosions involves controlling ignition sources and eliminating potential explosive atmospheres.