Backdraft

When material is heated enough, it begins to break down into smaller compounds, including flammable or even explosive gas, typically hydrocarbons.

[2] Characteristic warning signs of a backdraft include yellow or brown smoke, smoke which exits small holes in puffs (a sort of breathing effect) and is often found around the edges of doors and windows, and windows which appear brown or black when viewed from the exterior due to soot from incomplete combustion.

If firefighters discover a room sucking air into itself, for example through a crack, they generally evacuate immediately, because this is a strong indication that a backdraft is imminent.

Due to pressure differences, puffs of smoke are sometimes drawn back into the enclosed space from which they emanated, which is how the term backdraft originated.

The most common tactic used by firefighters to defuse a potential backdraft is to ventilate a room from its highest point, allowing the heat and smoke to escape without igniting.

ISO 13943[4] broadly defines flashover as a "transition to a state of total surface involvement in a fire of combustible materials within an enclosure."