名詞 oxygen mask:

1. a breathing device that is placed over the mouth and nose; supplies oxygen from an attached storage tank

1. If air is needed, the oxygen mask in the plane will pop down by itself.
   如果空氣缺乏，飛機(jī)內(nèi)的氧氣面罩會自動(dòng)放下。
2. An oxygen mask will come down from overhead in case of an emergency.
   若發(fā)生緊急情況，頭頂上會降下一只氧氣面罩。