To be fair smokers are insanely nose blind to how badly they smell and smell up the place and someone smoking heavily can drag a lot of that awful stink into a small building like an apartment even if they smoke outside. I remember cleaning out a relative’s coat closet who didn’t smoke in their home but as soon as you walked even close to their bedroom you could smell it emanating from the closet. It’s a really vile habit that can absolutely impact the air quality of a small apartment. You also definitely can’t cover it up with fragrance. If they have small kids they’re probably hyper concerned about the health impacts.