Eli5: How can they tell where a fire starts and how it grew after the building has already been burned down?

Question

Eli5: How can they tell where a fire starts and how it grew after the building has already been burned down?

In: 6

Answer 1

Material which has been doused with an accelerant burns hotter than the same material would otherwise. So in cases where an accelerant was used there’s often a visible as well as a chemical trail left behind.

An investigator once told me you could literally see the splash marks on the walls in blacker carbon) where a person had walked around with a can of fuel.