One word:
BUNK.
And I’m a former smoker, now strongly opposed to smoking.
This is a ridiculous PR trick. Nothing more.
There could be a situation in which surfaces that haven't been cleaned of the effects of smoke over the years have other kinds of cleanliness issues. The other thing is proper ventilation. Lots of disease is caused when pollutants get in heating/air conditioning units, and some of those pollutants will be smoke and tobacco related. Keep in mind that the problem isn't necessarily the tobacco; the additives could be. Another issue....fresh air and sunshine are necessary to kill germs.
I could see how a nonsense conclusion like this could be scientifically "proven" if all of those other factors are ignored.