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