Backdraft is defined as the sudden ignition of gases after introduction of air.

Backdraft is defined as the sudden ignition of gases after introduction of air.

• A. Gradual heating of surfaces without ignition
• B. A type of ventilation method
• C. Collapse due to structural failure
• D. Sudden ignition of gases after introduction of air.

Answer: (D)

Backdraft is about a rapid ignition that happens when air is allowed into a space that has been filled with hot, flammable gases. In a fire, heat drives off fuels and creates a dense layer of vapor and hot gases in a confined area, with limited oxygen so combustion stays incomplete. When a door or window is opened, fresh air rushes in and mixes with those gases. If the mixture reaches ignition conditions, it can ignite suddenly and violently. That matches the description of a sudden ignition of gases after air introduction. The other scenarios describe gradual heating without ignition, a ventilation method, or structural collapse, none of which capture this explosive ignition pattern.