( oxygen masks)
An oxygen mask is a device that is connected to a cylinder of oxygen by means of a tube. It is placed over the nose and mouth of someone who is having difficulty in breathing in order to help them breathe more easily.
N-COUNT
( oxygen masks)
An oxygen mask is a device that is connected to a cylinder of oxygen by means of a tube. It is placed over the nose and mouth of someone who is having difficulty in breathing in order to help them breathe more easily.
N-COUNT
Collins COBUILD Advanced Learner's English Dictionary. Английский словарь Коллинз COBUILD для изучающих язык на продвинутом уровне. 2006