What is a sign that a backdraft may happen during a fire?

The sign that a backdraft may happen during a fire is indicated by puffing of smoke at seams and cracks. This phenomenon occurs when there is a buildup of combustible gases within the structure that haven’t ignited yet. The puffing signals that a sudden influx of oxygen could lead to an explosive ignition, typical of backdraft scenarios.

When smoke is seen puffing out from the seams and cracks, it suggests that heated gases are being expelled from the fire area and that there is a potentially dangerous situation developing inside due to a lack of adequate ventilation. This is a critical warning sign for firefighters, as a backdraft can result when fresh oxygen is suddenly introduced to an area filled with unburned fuel and heat.

Other indicators do not provide the same warning of backdraft potential. For example, while visible flames might suggest a fire is active, they do not directly relate to the risk of a backdraft. Heavy rain prior to a fire is generally unrelated to combustion dynamics inside a structure, and clear air movement without resistance usually indicates ventilation rather than a risk of backdraft.