What is rollover and why does it signal a potential flashover risk?

• A. Rollover is flames spreading across the ceiling or roof surface; indicates unstable fire conditions and imminent flashover if not controlled.
• B. Rollover is flames spreading across the floor; signals collapse risk.
• C. Rollover is smoke pooling at the doorway; signals ventilation opportunity.
• D. Rollover is water steam buildup near the doorway; signals steam burns risk.

Answer: (A)

Rollover is when the flames ignite the hot, accumulated gases in the ceiling/upper smoke layer, causing flames to roll across the ceiling. This shows the fire has heated the upper layer to ignition temperature and the fuels in that layer are ready to flash, which means conditions are unstable and a flashover could happen suddenly if the fire isn’t slowed or cooled. Seeing rollover signals that the fire is transitioning toward a fully developed, room-wide involvement, so immediate action to cool and control the fire is needed to prevent a rapid spread. The other cues don’t describe rollover: flames on the floor indicate different, localized ignition; smoke pooling at the doorway points to ventilation effects rather than ceiling ignition; steam near the doorway relates to heat and steam production, not the ignition of the ceiling gas layer.