Stages Of A Fire

Stages of Fire

1. preheating
2. combustion

1. flaming combustion
2. glowing combustion
   3. extinction

Preheating

• water expelled from plants/wood
  • water can absorb a lot of heat, so material needs to be dry to burn
• due to flames nearby, drought, or long, hot summer day
• $pyrolysis:$ thermal decomposition of material
  • increased temperature
  • involves a change in chemical composition
  • chemical structure of the wood breaks apart and produces flammable hydrocarbon vapors
  • if oxygen is present it leads to ignition and combustion

Flaming Combustion

• fast and hot burning of pyrolized surface
• this is common during the early stages of fire
• this is where the greatest energy release occurs
• this is literally the flame
• in a flaming combustion, the fire is consuming the gases from the wood

Glowing Combustion

• the flaming front of the fire has passed
• it burns more slowly and at a lower temperature
• solid wood is now being consumed instead of pyrolized gases
• this is the back part of the fire, once it has passed
  • basically the coals left behind

Extinction

• the temperature drops or the fuel is used up
• the oxygen could also be cut off (if the fire is purposely extinguished)

Why Do We Care?

• they cause a risk of death and injury to people and animals
• property damage/destruction
• habitat destruction
• social disruption
• air pollution
• will become more common (and worse) due to climate change