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 happens when a fire burns in a confined space and hot, fuel-rich gases accumulate there with little usable oxygen. When air is suddenly introduced—such as by opening a door or window—those gases mix with the incoming oxygen. If the mixture is within the flammable range, it can ignite abruptly and violently, sometimes generating a pressure surge. This is the defining moment of a backdraft: the sudden ignition of accumulated gases after air enters.

This isn’t about gradual heating with no ignition, nor about a ventilation method itself, nor about structural collapse. It’s the rapid ignition of the trapped gases once air becomes available.