Smoke coming from cracks in walls and peeling or bubbling paint are indicators of a possible:

The correct answer is a concealed fire. This refers to a fire that is hidden within walls, ceilings, or other structural components and is not immediately visible. When smoke emerges from cracks in the walls and paint exhibits bubbling or peeling, it indicates that there may be heat and smoke accumulating behind those surfaces due to a fire that is not easily accessible.

These indicators suggest that the fire is not only present but may also be spreading, as the buildup of heat can cause materials such as paint to degrade and release smoke. Detecting such signs is critical for firefighters, as concealed fires can lead to sudden flare-ups and increase the risk of fire extension within the structure.

In contrast, flashover refers to a rapid spread of fire in a room, occurring when all combustible materials ignite almost simultaneously due to extreme heat conditions. Self-ventilating fire denotes a scenario where the fire has created its own ventilation path, which is often not directly linked to the observation of smoke from cracks and paint issues. An incendiary fire is one that is intentionally set, and while it may also produce signs like smoke and peeling paint, the characteristics outlined in the question are more indicative of a concealed fire.