What is backdraft?

• A. A sudden ignition of accumulated gases when air is introduced to a closed space.
• B. A type of rapid flame spread due to direct flame contact.
• C. A method of extinguishing a fire using water mist.
• D. A fire that only uses radiant heat.

Answer: (A)

Backdraft happens when a fire burns in a confined space and oxygen becomes scarce while a lot of highly flammable gases build up from the heated fuel. Those gases accumulate because the fire is ventilation-controlled, so you don’t see much flame yet but you do have a hot, gas-rich environment. When air is suddenly introduced—like when a door or window is opened—oxygen mixes with those gases, and the mixture can ignite violently, producing a rapid, explosive flame surge. This is the dangerous moment firefighters fear when they ventilate a room too soon or too aggressively.

The other ideas describe different fire behaviors or methods. A rapid flame spread from direct flame contact isn’t backdraft; backdraft specifically involves ignition of built-up gases after air returns. Water mist is a tool for extinguishing, not a description of backdraft. A fire that relies only on radiant heat isn’t about a sudden ignition of trapped gases.