In which scenario should you not ventilate during a backdraft situation?

Ventilation during a backdraft situation is crucial to manage the hazards associated with rapidly changing fire conditions. Not ventilating when the fire is completely extinguished is appropriate because there is no longer a risk of combustion or explosion, which typically accompanies a backdraft scenario. Since a backdraft occurs when oxygen is suddenly introduced to a fire that is consuming unburned gases, the absence of active fire means there is no potential for a backdraft event.

In situations where gas is detected inside or where there are clear signs of a backdraft, ventilation could worsen the situation by introducing oxygen to an environment already filled with flammable gases, increasing the risk of an explosive atmosphere. Additionally, visible flames outside a structure may indicate active fire conditions, which also necessitate careful ventilation strategies to mitigate the dangers of backdrafts or flashover. Therefore, complete extinguishment of the fire is the only scenario where ventilation is unnecessary and safe.