How do firemen know the cause of a fire after everything has burnt down?

Question

Often times you hear about the cause of a fire being a cigarette for example. However, isn’t the cigarette already long gone after the house/forrest/etc. has burnt down? How is it still possible find out what started the fire?

In: 567

Answer 1

I heard a park service ranger talk about how they trace the origin of wildfires.

Grasses when burning tend to bend over in the direction the flames come from. So the residue points towards where the fire originated. Just follow the direction the grass points and you’ll find the origin, and then look for evidence of a source – a cigarette butt, a campfire ring, residue from chainsawing, or shell casings that indicate maybe someone fired a round that created a spark. Lightning strikes leave their own mark.