Smoky Smell

[Celticlassie]

We bought a house a few months ago and since then there has been a sporadic smoky smell (cigarette). It comes and goes - sometimes we can go weeks without smelling anything, but then it comes back quite strongly. The house is a semi detached converted bungalow and the smell seems to come from upstairs. I don't believe the prev tenants were smokers (or so they claimed) and the downstairs isn't smoky. We've not changed the carpets upstairs yet, but I've had my face down sniffing them and am not getting smoke from there. If it was the neighbours I feel it would be more consistent?
We open windows as often as possible (for Scotland) and sometimes use a scented candle, but it still comes back.

Any ideas what it could be, or how to get rid of it for good?

Ta in advance.

it a ghost, obv.

As I suspected.

Do next door smoke? (Or have a regular visitor who might smoke inside or outside?)

I have no idea if they do (although can imagine that they might) but it seems like it would be all the time if they did. Could be a visitor. It sometimes smells a little like weed too.

Smells can drift in strange ways according to the way air currents move around buildings. If, say, they had a son/friend/etc who was popping round to see them but also popping outside for the occasional smoke, I can imagine that any smell might well drift upwards. Especially if it's regularly coming at a certain time of day or in certain weather conditions.

Sorry. That should read 'Especially if, when it did smell, it was coming at.....

When I moved into my old flat, one of the rooms had a really smoky smell and it was coming from my neighbours flat. There was a ventilation vent in the wall and the smell was coming through the wall. We ended up taping up the vent and the problem was solved. We noticed it very strong in the evenings (when he was home from his work)

Yes - there's that also. (Air leaks between the houses.)

Was hoping it may be historical, but you've confirmed my fears that it probably isn't. Thank you!