How do they film minors smoking?

Many movies depict children and minors (and non smoking actors) actively smoking a cigarette and blowing actual smoke. How is that done?

Answer

Actually the film makers claim that the cigarettes used by the minors are tobacco-free cigarettes or nicotine-free cigarettes. They are commonly called herbal cigarette.

According to wikipedia,

Herbal cigarettes are also used in acting scenes by performers who
are non-smokers, or -- as is becoming increasingly common -- where
anti-smoking legislation prohibits the use of tobacco in public
spaces.Herbal cigarettes are not viewed as physically addictive, as they do not contain addictive substances.