What type of fire and smoke indicates that an evacuation may be necessary?

The indication that an evacuation may be necessary is highlighted by the risk of flashover due to combustible build-up. Flashover is a rapidly spreading fire that occurs when the temperature in a contained space rises to the point where all combustible materials ignite simultaneously. This condition presents a high level of danger not only because of the intensity of the fire that can quickly develop, but also because it greatly limits the time available for passengers and crew to evacuate.

In a scenario where there is a significant build-up of combustible materials, it suggests that the fire is not only more likely to grow but may do so uncontrollably. This makes immediate action crucial. Recognizing this risk can help the crew prioritize evacuation efforts to ensure safety in a potentially life-threatening situation.

Other types of fires mentioned, such as electrical fires or smoldering smoke, may still pose significant risks, but they do not inherently indicate that an immediate evacuation is necessary to the same extent as the risk of flashover. Likewise, cooking fires, while they can be dangerous, are often manageable and might not require evacuation unless they escalate beyond control. Therefore, the presence of combustible build-up leading to flashover is a critical factor that necessitates swift evacuation action.