I once lived in a second floor apartment where I would smell smoke from time to time. I finally realized that it was because the people below me used a charcoal grill right under the staircase, and all the smoke rose up into my apartment. I asked them nicely once to move their grill out away from the building, and they did. A few days later, I noticed that they had lit more coals right under my apartment again, and nobody was outside watching the grill. I dumped the grill on the ground right in front of their front door, and never had problems again.