Final answer:
The passenger mask doors automatically open at a cabin altitude known as the deployment altitude, typically set at 14,000 feet above sea level. The oxygen masks drop down from the overhead compartments in the event of a rapid decompression or loss of cabin pressure, providing passengers with access to oxygen for survival.
Step-by-step explanation:
In an aircraft, the passenger mask doors automatically open at a certain cabin altitude. This altitude is known as the deployment altitude and is typically set at 14,000 feet above sea level. When the cabin altitude reaches this level, the doors of the passenger oxygen masks open, allowing oxygen to be released for the passengers to breathe.
At high altitudes, the air is thinner and contains less oxygen. In the event of a rapid decompression or loss of cabin pressure, the oxygen masks drop down from the overhead compartments automatically. This ensures that the passengers have access to a source of oxygen, which is necessary for survival. It's important for passengers to wear the masks properly and secure them tightly to their faces, as they provide the necessary oxygen to breathe in the event of an emergency situation.