Which of the following are indicators of flashover?

Choosing surface burning, burning from above, and demarcation line as indicators of flashover is significant because these characteristics provide tangible evidence of the rapid transition from smoldering combustion to a fully developed fire.

During flashover, conditions in a room reach a point where the flammable gases and materials ignite almost simultaneously. Surface burning refers to flames that have spread across the surfaces of combustibles. Burning from above indicates that superheated gases are igniting materials near the ceiling, further illustrating the intense heat and energy release typical of flashover situations. The demarcation line is a visual cue often seen during flashover events, where the cooler and hotter areas within the space are distinct, typically marked by a clear temperature gradient.

These signs collectively indicate that the fire has gained sufficient heat and buoyancy, leading to a rapid increase in fire behavior and danger. Understanding these indicators allows fire investigators and responders to assess the fire's intensity and potential spread, informing their strategies for firefighting and investigation. In contrast, other options may represent signs of heat or fire activity but do not encapsulate the full suite of indicators that define the critical moment of flashover effectively.