One of the most difficult odors to get out of a home is that of tobacco smoke. If you look online, you can probably find thousands of horror stories of homeowners that bought a home not realizing that they would be dealing with this issue for a long time to come. The problem is that the smoke molecules are so tiny they make it into every crack and crevice in your home, and usually there is a film left behind that will keep the smell lingering for a long time.
If you really want to get rid of it, there are a few things that you can try, but in reality, it comes down to a thorough cleaning, often several times. Even lightbulbs can be a problem. When they are lit up, the film left behind from the smoke gets heated up and the smell comes back. Another thing is HVAC filters as well as other replaceable filters you might find in your home. These can hold a large amount of smoke in them, leading to a problem with odors later on.