Secondhand smoke, also known as environmental tobacco smoke (ETS), is a mixture of the smoke given off by the burning end of a cigarette, pipe or cigar and the smoke exhaled from the lungs of smokers.

• 二手烟，又被称为环境香烟烟雾（ETS），是由香烟，烟斗，雪茄，或是吸烟者肺部发散出来的烟雾混合体。