In Action movies, I have seen a couple of times that if flammable gases or liquids like benzene are ignited, the fire spreads out within fraction of a second and sometimes there is also an explosion. However, if a Piece of wood in a grill is lightened, it may take minutes if the fire has the full Magnitude. Why there is a difference in ignition Speeds (what is the physical cause)?
Are there kinetic equations how to determine the Speed how fast a fire would spread out?
I am interested in the viewpoint of thermodynamics how to derive the Speed of ignition.