When should oxygen masks be deployed?

The deployment of oxygen masks is essential when cabin pressure drops or when the air quality is compromised, as this situation can significantly impact the safety and well-being of everyone on board. Under normal cabin pressure conditions, the air is breathable and suitable for passenger and crew needs. However, if there is a sudden loss of cabin pressure—such as during a rapid descent or a structural failure—oxygen masks provide supplemental oxygen to ensure that individuals can breathe adequately despite the lower air pressure.

Furthermore, if there are hazardous situations that affect air quality, such as smoke or harmful fumes, the use of oxygen masks becomes crucial to prevent hypoxia, a condition caused by insufficient oxygen reaching the brain. This proactive measure is a standard safety protocol, aimed at maintaining oxygen levels capable of sustaining life until the aircraft can return to a safe environment or altitude.

While the other options may suggest various scenarios for mask deployment, they do not align with the standardized safety procedures that prioritize passenger health and safety in emergencies. For example, masks are not deployed just at the start of a flight or merely upon request, as this could lead to situations where passengers are left vulnerable during critical moments.