What is a warning sign of backdraft?

A warning sign of backdraft is smoke puffing from the building. This behavior indicates that there is a buildup of hot gases within the room or structure that are being expelled in short bursts. The puffing occurs when the pressure changes due to the oxygen entering the space, creating the potential for a fire to ignite violently when the trapped gases are suddenly exposed to a fresh air supply.

Recognizing this sign is crucial for firefighters, as it signals an unstable environment that may lead to a backdraft, where an explosive ignition of the superheated gases can occur if not handled carefully. This behavior of smoke can alert firefighters to take necessary precautions before entering the building.

In contrast, heavy smoke at the base of the fire typically indicates that the fire is in an advanced stage, rather than a sign of imminent backdraft conditions. A sudden quiet in the fire's sound may imply that combustion is stalling but does not specifically indicate backdraft potential. Fire burning through the roof generally suggests that the fire is venting, which might not provide useful information about backdraft occurrence in the immediate area below.