Rollover is a sign that _______ is imminent unless actions are taken to change the fire conditions.

Rollover is a phenomenon that occurs in the early stages of a fire when unburned gases in the upper atmosphere ignite, producing flames that move across the ceiling. This is a critical indicator that flashover, a rapid and widespread ignition of all combustible materials within a space, is imminent.

In this scenario, the presence of rollover suggests that there is an accumulation of heat and combustible gases, and if the conditions are not altered—such as by cooling or ventilating the space—the risk of a flashover occurring becomes significantly higher. Flashover can lead to a sudden and intense increase in fire intensity, posing extreme dangers to both occupants and firefighters.

Other options, while related to fire behavior, do not accurately reflect the imminent danger indicated by rollover. For example, backdraft occurs when oxygen is suddenly introduced into a fire that is smoldering due to a lack of oxygen, leading to an explosive event. The decay stage indicates a reduction in the fire's intensity as fuel is exhausted. A smoke explosion can occur if combustible gases, typically smokey and rich in flammable materials, ignite. However, these phenomena do not directly correlate with the immediate risk presented by rollover like flashover does.