Because you can still smoke "in your own home." You can't subject your neighbors to smoke in a multi-unit building.
> I wonder if your building is up to code?
Certainly, as of the 1920s, when it was built. I don't think that new buildings (at least those built with fire-resistant wood frames, which is the current trend) are really better at preventing smells from moving between units anyway.
Please move! It only takes one mistake by your neighbor to start a fire and you will have very little time to react.
My concern about code is because there should be a minimum fire resistance rating between floors. The fact that you can see the smoke through your floorboards when your neighbor burning incense makes me think that there is no such barrier.
Home means more than single family dwelling....
Edited to put my more important thoughts up top and my mundane reply to the thread at the bottom.
Because you can still smoke "in your own home." You can't subject your neighbors to smoke in a multi-unit building.
> I wonder if your building is up to code?
Certainly, as of the 1920s, when it was built. I don't think that new buildings (at least those built with fire-resistant wood frames, which is the current trend) are really better at preventing smells from moving between units anyway.