The Stages of a Fire

By most standards including the International Fire Service Training Association (IFSTA) there are 4 stages of a fire.  These stages are incipientgrowthfully developed, and decay.  The following is a brief overview of each stage.

INCIPIENT STAGE
  • Earliest of the four phases of a fire.
  • Development of a fire is largely dependent on the fuel involved
  • Fire can be controlled or extinguished by portable fire extinguishers
  • No detectable flame at this stage
  • Smoke particles are released into the atmosphere.
  • The layer of hot gases becomes more clearly defined and increases in volume
  • The fire nears the growth stage.
GROWTH STAGE
  • Earliest stage of a fire beginning with actual ignition.
    • Fire limited to origin of ignition material.
    • Flame temperature may be well above 540°C.
    • Some heat being generated. Amount of heat will increase with the progress of the fire.
    • Sufficient oxygen and fuel are available for fire growth to a point where total involvement is possible.
    • Heat carried to uppermost region of confined area.
    • Heated gases spread laterally from the top and then down.
    • Cooler air forced to lower levels.
    • Upper region can exceed 700°C.
FULLY DEVELOPED STAGE
  • – All combustibles in the space have reached their ignition temperature.
  • – Burning rate limited by the amount of oxygen available in the air for combustion.
  • – Unburned fuel in the smoke may burn as it meets fresh air in adjacent compartments.
  • – Structural damage to exposed steel normally occurs.
  • – Normally inaccessible by hose teams.
  • – Best fought using indirect attack.
DECAY STAGE
  • Available oxygen is consumed or reduced to a point where there is insufficient oxygen to react with fuel.
  • – Flame may cease to exist if the area is sufficiently airtight.
  • – Burning reduced to glowing embers
  • – If fire continues to smolder, compartment will fill with dense smoke and gases and temperatures could reach well over 10000C.
  • – Intense heat and high concentration of fire gases could produce suitable conditions for a backdraft explosion.