How Long Does Oxygen Mask Last?
At all times, pilots wear an oxygen mask while flying in an aircraft. Passengers are not required to wear one since the plane’s oxygen level is artificially maintained to provide good breathing.

The need to use masks may become necessary if the cabin becomes depressurized at high elevations, as it would be dangerous to lose consciousness. Oxygen masks can last 10-15 minutes. The pilot would have decreased the plane’s altitude for suitable breathing during this time.