A properly designed smoking area should be unnoticeable in that no smoke should leak out into the non-smoking area.

An example from many years ago: I was on a flight transiting NRT to PEK. NRT was, for the most part, a very clean and nice airport. PEK was the old airport, and it obviously looked old and shabby (the new one was being built).

However, NRT had smoking areas that were open to surrounding area where smoking was not allowed, which meant that non-smokers had to walk through the smoke escaping from the smoking areas whenever they passed by the smoking areas. PEK, on the other hand, had enclosed smoking rooms with the ventilation set up so that the air would always blow into the smoking rooms if the door was opened.

Unfortunately, most smoking areas within restaurants and other buildings when smoking was allowed were more like NRT back then in that if you were in the non-smoking area near the smoking area, you were effectively in the smoking area, except that you couldn't smoke. Meaning the worst situation for both non-smokers (who would be annoyed by the smoke drifting over from the smoking area) and smokers (who were not allowed to smoke there).