What are classic indicators of a potential backdraft before opening a door?

• A. Thick, dark, stagnant smoke; no visible flame; signs of pressurized gases behind the door.
• B. Thin, wispy smoke with active flame.
• C. Heavy rainfall outside the structure.
• D. A strong citrus odor.

Answer: (A)

Backdraft happens when a fire in a closed space fills the room with hot, fuel‑rich gases but little fresh air, so the fire can’t sustain itself until air suddenly becomes available. The telltale signs you’d notice before opening a door are dense, dark, stagnant smoke and little to no visible flame, along with indicators that gases are building up behind the door—like the door or surroundings feeling hot or bulging and smoke staying pooled rather than flowing freely. These cues signal that a sudden influx of air could ignite the amassed gases explosively if the door is opened.

The other options don’t fit because thin, wispy smoke with active flame shows the fire is already ventilating and burning with oxygen, not in a backdraft state; a heavy rainfall outside or a citrus odor isn’t related to how backdraft manifests.