When does rollover occur in a fire?

• A. Growth stage
• B. Fully developed stage
• C. Decay stage
• D. Initial ignition

Answer: (A)

Rollover is the ignition of the flammable gases that have collected near the ceiling, creating a flame layer that rolls along the top of the room. This happens during the growth stage when heat release causes the upper layer of hot, buoyant combustion products to build up and mix with air until they ignite. At this point the fire is intensifying and spreading, but the space isn’t yet fully involved, so the rollover appears as a ceiling-wide flame front rather than a room-wide burn. As the fire moves into the fully developed stage, the space is already engulfed and rollover is less distinctive; in the decay stage the flames fade and rollover is no longer a defining feature. So, rollover best fits the growth stage.