Mountain climbers often carry oxygen tanks because the air is very thin at high altitudes. 登山者通常会携带氧气筒，在极高的地带空气相当稀薄。
As I was seated in the waiting room for an appointment with my doctor, a lady came in carrying a portable oxygen tank with tubes connected to her nose. 我坐在医生的候诊室里等候着，一位手提小型氧气筒的女士走进来，几条凌乱的胶管从氧气筒连到她的鼻孔里，这女士口中偶尔的发出喃喃咒语。
