What does smoke puffing in and out of a building indicate?

• A. Conduction
• B. Backdraft conditions
• C. Convection
• D. Radiation

Answer: (B)

Smoke puffing in and out signals backdraft conditions. In a closed or poorly ventilated space, a fire can heat and fill the room with hot, fuel‑rich gases while oxygen runs low. When a door or window is opened, fresh air rushes in and mixes with those gases, potentially igniting violently and producing a brief outward and inward puff of smoke. This is a warning that a sudden, dangerous ignition or explosion could occur if ventilation is not managed carefully. It’s not about general heat transfer like conduction, convection, or radiation—the puffing shows a rapid air–fuel interaction inside a hot compartment.