What is backdraft and what exterior cues might suggest it is imminent?

What is backdraft and what exterior cues might suggest it is imminent?

• A. A sudden, dramatic change in interior temperature with no exterior warning signs.
• B. Dense, light smoke that clears when a door is opened.
• C. A gradual cooling of interior air after ventilation.
• D. A rapid ignition of accumulated gases when air enters a volume; cues include dense, dark smoke and a sudden flame outburst upon opening a door or window.

Answer: (D)

Backdraft is the rapid ignition of accumulated, vent- trapped gases when air is introduced to a fire-filled space. When a door or window is opened, fresh air rushes in and can mix with the hot, fuel-rich gases, causing a sudden and violent ignition that may push flames and smoke out of the opening. Exterior cues that suggest an imminent backdraft include dense, dark smoke gathered at the exterior opening and a sudden flame outburst or flash when the opening is created (for example, when a door or window is opened). These signs indicate that a large amount of unburned gases are present and can ignite quickly once air is reintroduced. Other described scenarios don’t fit backdraft as well: a sudden interior temperature change with no exterior warning signs isn’t specific to backdraft; light smoke that clears upon opening a door suggests ventilation clearing smoke rather than gas ignition; and a gradual cooling after ventilation describes a decreasing fire environment, not an explosive ignition event.

Backdraft is the rapid ignition of accumulated, vent- trapped gases when air is introduced to a fire-filled space. When a door or window is opened, fresh air rushes in and can mix with the hot, fuel-rich gases, causing a sudden and violent ignition that may push flames and smoke out of the opening.

Exterior cues that suggest an imminent backdraft include dense, dark smoke gathered at the exterior opening and a sudden flame outburst or flash when the opening is created (for example, when a door or window is opened). These signs indicate that a large amount of unburned gases are present and can ignite quickly once air is reintroduced.

Other described scenarios don’t fit backdraft as well: a sudden interior temperature change with no exterior warning signs isn’t specific to backdraft; light smoke that clears upon opening a door suggests ventilation clearing smoke rather than gas ignition; and a gradual cooling after ventilation describes a decreasing fire environment, not an explosive ignition event.