Why do firefighters cut holes in the roof of a building on fire?

This is called "venting the roof." There are two basic reasons for this practice. Dangerous gasses and dark smoke accumulate in a burning building. It is impossible for firefighters to see in this environment. When a hole is made in the roof, the smoke and gases escape. Venting the roof makes it easier for firefighters to see and find the source of the fire, and it also reduces the possibilities of backdraft and flashover. Another reason for venting the roof is to see how far the fire has progressed. One of the fastest avenues through which fire is spread is the attic. Heat and smoke rise to the attic where the fire can move quickly. Firefighters may go ahead of the fire and cut holes in the roof to release the heat and stop the fire from spreading through the attic.