What is an indication of fire risk in the cabin?

An activated smoke detector is a critical indication of fire risk in the cabin, as it is specifically designed to alert crew members about the presence of smoke, which is often a precursor to fire. Smoke detectors work by sensing particulates in the air that are associated with combustion. When they detect these particulates, they activate an alarm that draws attention to a potential fire hazard, allowing the crew to take immediate action to address the situation.

While visible smoke is indeed a significant indicator of fire, it suggests that a fire has already started or is advancing. An activated smoke detector, on the other hand, serves as an early warning system that can prevent a situation from escalating. Options related to circuit breakers or low power supply do not directly indicate fire risk in the same way, as they relate more to electrical issues rather than indicating the presence of smoke or fire directly.