Passive smoking

Inhalation of tobacco smoke by persons other than the intended active smoker

Passive smoking is the inhalation by individuals other than the smoker of tobacco smoke, called second-hand smoke, passive smoke (SHS) or environmental tobacco smoke (ETS). It occurs when tobacco smoke diffuses into the surrounding atmosphere as an aerosol pollutant, which leads to its inhalation by nearby bystanders within the same environment. Exposure to passive tobacco smoke causes many of the same health effects caused by active smoking, although at a lower prevalence due to the reduced concentration of smoke that enters the airway.

From Wikipedia, under CC BY-SA. More on occurri.