I once worked in an carpetted office where 'everybody' smoked and had done so for 40 years. Not surprisingly the office smelled of it (vile). Then came the ban on smoking in public places. Remarkably the smell had reduced in about 3 months until it was un-noticeable. I suggest a new pollen filter and time.

The laws of chemistry and physics mean that if you can smell something, that something is airborne, so if you wait long enough the source will disappear. The question is how long you are prepared to wait. Clearly, more ventilation and raising the temperature will speed the process. Otherwise do as already suggested.

The dealer (deadlier?) should have removed any stains, which are not volatile and therefore more permanent. When we moved to our present place it had been owned by smokers - the smell had gone but the stains needed more work.

I have quite a few customers who smoke but there is one elderly lady who springs to mind. She would be in her late 70's i'd guess, and is, for all intents and purposes, a chain smoker. Sometimes if the weather is nice the front door will be slightly open and the stink of cigarettes coming from inside the house is almost overwhelming!. Also, she pays me cash, and when i am sorting my cash takings out at the end of the day, week, or when i am away to do some banking. i can immediately identify her £10 note!.

On another note more relevant to the post, years ago i worked as a car valeter at a Saab dealer. One time this old 900 got traded in and it absolutely stank of cigarettes. The head salesman, a Glasgwegian (who was an arrogant so and so and thought he knew everything) declared that he knew exactly how to deal with the smell, going on about and old car valeter showing him this 'trick' years previously. The essence was to light a fire (in some reasonably safe receptacle) using cardboard, then extinguish the flames while leaving it smouldering, put it inside the car with all the doors and windows shut, leave it for half an hour so the car completely filled up with smoke. Then open it all out, getting rid of the 'smoke machine'. According to the salesman, what would happen is that the car would stink of the smoking cardboard for a while, but when it dissipated it would take the cigarette smell with it. It didn't though, it stank of burning cardboard for a while, then went back to stinking of cigarettes!