What is backdraft and what are two warning signs?

• A. Backdraft is the ignition of accumulated, oxygen-depleted gases when air enters; signs include pressurized, dark smoke pushing from openings and a sudden heat increase or puff when a door or window is opened.
• B. Backdraft is a ventilation technique to remove smoke.
• C. Backdraft is a sudden flash of flame only at the ceiling.
• D. Backdraft is cooling of hot gases by water.

Answer: (B)

Backdraft happens when a sealed or heavily compartmented space has hot, fuel-rich gases with little oxygen. Those gases can’t burn in that oxygen-poor state, but when fresh air is suddenly introduced—by opening a door or window, for example—the mixture can ignite violently, causing a rapid flash of flame and a surge of pressure.

Two warning signs to recognize are: first, pressurized, dark smoke being pushed out of openings, often with little visible flame; second, a sudden heat increase or a puff of flame when air enters the space, such as when a door or window is opened.

The other options don’t fit backdraft: it’s not a ventilation technique to remove smoke, it’s not limited to a ceiling flash, and it doesn’t involve cooling hot gases with water.