an item that is placed over the mouth and nose and provides oxygen.
He had removed his helmet and oxygen mask and was trying to get out in the normal manner.
Passengers on the plane quickly secured their oxygen masks when cabin pressure suddenly dropped.
The firefighter donned an oxygen mask before bravely entering the smoke-filled building.
The pilot calmly instructed everyone to remain seated while demonstrating the use of the oxygen mask during the safety briefing.
Hospital staff trained in emergency response are familiar with the proper fitting and use of an oxygen mask.
