Many years ago I when I was undoubtedly young, I worked for a company where it seemed like everybody smoked, but this was back when you could smoke indoors; My bosses used to smoke like crazy in the section of the building where I worked, and but the thing was, even when my bosses were not near me, or if they were not smoking, I would still breath fresh smoke throughout the day.
This was because the Heating, Ventilation plus A/C system in the building would be moving smoke from where other people were smoking who knows where, right to my nose, through the air ducts.
This would be whenever the heating or the air-conditioning went on, and throughout most of the year you usually needed 1 or the other of course, however forget an air quality system, this was the opposite of that, however i started getting a minor cough within weeks of working there. I used to smoke a little myself before I started working there. But that locale cured myself and others of ever wanting a cigarette again undoubtedly soon. The need for air duct cleaning in that locale was crazy. Nobody else noticed because they were smokers. The worst section is that you could not open the windows undoubtedly much if at all periodically, because we were high up in a skyscraper; So we were just stuck with this smokey air. I always thought I would quit 1 day because of the terrible air quality. I would go lake house periodically and I would suppose sick from the air for hours. In the end, I left for a unusual reason, but when I left I was cheerful never to breathe that air ever again.