Stages of combustion: flaming stages (see pictures from lab)
Pre-heating � temperature of the fuel is raised to the point where gases start to volatize
Pre-ignition � volatile materials in the fuel are vaporized
Flaming � the ignition temperature of the fuel is reached and combustion begins
Transition � fuel is partially consumed by combustion while flaming continues in portions of the fuel resulting in initiation of smoldering and smoke generation
Smoldering � combustion of the fuel is essentially complete where oxygen is available and smoldering continues resulting in smoke generation
Glowing � a stage of combustion where oxygen is limited
The four most important stages of combustion for prescribed burners are,
pre-ignition (fuel is about to burst into flame)
flaming � active combustion
transition � smoke generation begins
smoldering � residual smoke production