What must be checked about the smoke detector during a toilet check?

The correct approach during a toilet check regarding the smoke detector is to ensure that it must not be blocked or tampered with. This requirement is crucial for maintaining safety on board an aircraft. Smoke detectors serve as a primary safety mechanism to detect smoke or fire, which is essential for passenger and crew safety. If the detector is blocked or tampered with, it may fail to operate effectively in the event of a fire, which could lead to catastrophic consequences.

Ensuring that the smoke detector is unobstructed allows it to function properly, providing an immediate alert in the case of smoke or fire, allowing for timely intervention. This practice is part of the broader Crew Resource Management and Safety protocols that emphasize proactive measures to ensure compliance with safety regulations and the protection of all individuals on board.