SAG-AFTRA has strict guidelines about the use of cigarettes on set. Auditions must state whether smoking is required, and every employment contract includes a section that indicates whether an actor will be working in any kind of environment with smoke, including the artificial kind. Union contracts guarantee actors additional daily compensation for working with smoke. Producers must also provide every performer working around prop cigarettes with a Material Safety Data Sheet. Because of these regulations, many productions use prop cigarettes and prop smoke to create the illusion of real smoking.
Good thing the labour union comes to the rescue.
https://www.backstage.com/magazine/article/do-actors-really-smoke-75370/
Unions are awesome!