Simple separation of smokers and non-smokers within the same airspace may reduce, but does not eliminate, exposure of nonsmokers to environmental tobacco smoke.
Environmental tobacco smoke (ETS) is dirtier than the smoke that is inhaled in a cigarette because it is not filtered. The filter on the end of a cigarette removes some the harmful chemicals. ETS is the largest source of indoor air pollution. Restaurants that allow smoking can have six times the pollution of a busy highway.