I have the same problem. The guy below me smokes like a furnace and I have tried everything.
I tried Kenmore Air purifier and it did not work for my apartment because of its size and design. I have 990 sq feet and its wide open...So unless I purchase 2 or three air purifiers I am out of luck.
It's really a shame....because people have a right to smoke and we don't have a right not to breath it.