Sorry for the long post!
I rent a second floor apartment in a 3 apartment house. We each have our own forced air furnace (oil) in the basement and my apt has 8 heat registers and one return (wall). I have tried tracing the ducting in the basement but cant really see if we share a main connector or not - or would it be more likely that we share ducting which is not visible in the basement?
Sorry I realise this must sound like a strange question, the reason I ask is that I am having a potential secondhand smoke issue from the downstairs apartment and this is my first time living with a forced air furnace (I'm from a warm country originally which does not need a lot of heating so i dont know one end of a furnace from the other).
My landlords who are great live downstairs and are smokers - I was not aware of this at the time I moved in (they were sick and not smoking) and I cant afford to move but am concerned because I have strong family history of lung and heart disease. I have done alot of work around the apartment sealing around pipes, doors etc.. to cut down on air transmission between our apt's but the one place I still get a stale smoke smell from is the heating ducts particularly on windy days. Occasionally last winter when i would first turn on the heat I would get quite a strong smoke smell, but not always (a previous tenant was a smoker many years before). I have cleaned all the registers which were full of dust and soot and have bought electrostatic filters to go on the outside of the vents for this winter (it says not use them on all vents unfortunately) - if we don't share air ducting it must be residual smoke left over from previous tennants and an old furnace which i can deal with by further cleaning and sealing, but if we share air ducts this is going to be an ongoing problem. I have tried to tactfully raise the issue of air transmission between apts, but they can't smell it and i don't want to offend them by being blunt particularly as it is their home.
Any suggestions about what I can look for between our furnaces or things I could try to seal around the vents would be greatly appreciated.