Final answer:
Pressing the smoke reset button outside an airplane lavatory wall is part of the safety protocol to reset the smoke detection system after ensuring no fire hazard exists, clearing the alarm and associated emergency procedures.
Step-by-step explanation:
When the smoke reset button outside of the lavatory wall is pressed in an airplane, it serves as part of the aircraft's smoke detection system, designed to ensure safety and address any incidents involving smoke.
The smoke reset button allows the crew to reset the smoke detection system after a smoke alert has been investigated and it has been determined that there is no fire hazard.
Flight attendants typically have the authority to press this button, and it is often a protocol to do so only after a thorough safety check has been conducted.
Pressing this button should clear the alarm, halt the strobing of the associated indicator light, and also deactivate any automatic emergency procedures that were initiated, such as the release of fire-suppressants.
It is crucial that this button is used correctly to maintain onboard safety and to avoid unnecessary complications that can occur if a false alarm is reset without proper investigation.