How do the workplace no smoking laws affect TV studios and film sets, where smoking is part of the narrative?

Taken to one extreme, if a non-smoking person (like Roy Castle) became ill with a smoking-related illness after working exclusively on smokey film sets, would that force a change in the law.

Or, conversely, could you set up a webcam in a 1970s-styled office with the aim of producing a performance art piece (if a runner can be performance art, why not the day-to-day runnings of an office) and thus allow smoking on the same grounds as a film set?