Passive smoking

inhalation of smoke by persons other than the intended active smoker

Someone smoking a pipe or a cigarette will exhale tobacco fumes. People who are physically close to the smoker will inhale these fumes. This is called passive smoking. Even though passive smokers don't some themselves, they are still affected by the smoke. The effects of inhaling tobacco smoke are similar to those of smoking. These effects were first studied in the 1970s. Since then, many countries have made laws that limit who is allowed to smoke, and where smoking is allowed. As an example, many countries made laws that forbid smoking in restauarants, to protect the staff against the effects of passive smoking.

Smoke in an Irish pub, before a smoking ban in pubs came into effect.