Drrr fire triangle

• The fuel is the material that burns, such as wood or paper.

  
• Heat is necessary to start and maintain the chemical reaction between oxygen and fuel.
• Oxygen is required to sustain combustion, which can come from air or other sources.
• Fire triangle


  The three elements needed for fire to occur: heat, fuel, and oxygen

  
• Fuel


  • Any combustible material in any state of matter - solid, liquid, or gas. Most solids and liquids become a vapor or gas before they will burn
• Oxygen


  • The air we breathe is about 21% oxygen - fire requires at least 16% oxygen
• Heat


  • The energy necessary to increase the temperature of the fuel to a point where sufficient vapors are given off for ignition to occur
• Fuel


  • Clothing
  • Furniture
  • Curtains
  • Flammable liquids
• Heat


  • Stoves
  • Heating appliances
  • Fireplaces
  • Damaged wiring
• Each of the three elements (fuel, oxygen, heat) must be present at the same time to have a fire. A fire will burn until one or more of the elements is removed
• Fire


  The rapid oxidation of a fuel evolving heat, particulates, gases and non-ionizing radiation
• Fire tetrahedron


  • Oxygen
  • Fuel
  • Heat
  • Chain reaction
• Chain reaction


  All areas of the fire tetrahedron must be present for a fire to start
• No chain reaction


  • A plug shorting out, producing a spark but not a fire
  • Using alcohol to cook with (in most cases)
  • Dropping a lit cigarette on the counter top and picking it up
• Spontaneous combustion


  Internal combustion arising with no external energy when all four parts of the tetrahedron are present, even if they don't physically appear to be
• Conduction


  • The only means of transferring heat to the interior of fuels (wood, litter, duff)
  • Transfer of heat from one molecule to another
  • Example: touching your hand to a hot object

  
• Radiation


  • Transmission of heat by electromagnetic waves
  • Examples: heat from sun, fireplace, stove
  • Contact between radiation source and affected body not necessary
  • Example: preheating of fuels ahead of fire front
  • Absorption of radiation by woody fuels - only by thin layer at surface (rest by conduction)

  
• Convection

  • Transfer of heat by movement of a gas or liquid (air)
  • Hot air moves vertically (exceptions: winds, slopes)
  • Examples: heating a pot of water, smoke from a fire
• Flames are brought closer to the fuel due to slope

  Increases heat transfer
• Wind


  Pushes the flames over, bringing them closer to the fuel, increasing heat transfer