Jon, On the radio last week you gave someone a remedy to get rid of a smoker's odours coming up through the apartment building. Could you please post that for me. Francine.
First my opinion -- second hand smoke from cigarettes is already identified as a public health problem, and is often banned in apartment buildings. Second hand smoke from cannabis, although delightful for some, is a serious health problem for others, especially young children. The law is allowing apartment owners to install cannabis bans, although it may take longer to make that work than it took to legalize pot. I would ask anyone who finds their smoke is affecting neighbours to go for non-smoking forms of pot while in their apartment and not impose their health choices on others.
Now for a building technology answer to the question.
When an apartment building does not have a central ventilation system, each apartment is on its own – and your neighbours odours can easily find their way through the walls and floors into your apartment. The best solution, but rarely practical, is to air seal the entire party wall(s), floors and ceiling – isolating your apartment from the air of all the others. That is not an easy thing to accomplish, especially in an older wooden building.
The next best is to profit from the fact that the ventilation industry has developed ventilation machines (HRV: https://www.joneakes.com/jons-fixit-database/887-WHAT-IS-AN-AIR-TO-AIR-HEAT-EXCHANGER-HRV-and-ERV) for apartments. These smaller than usual machines have two fans, one which brings in fresh air and another that takes out stale air – and they are usually perfectly balanced. When you are struggling with odours from neighbours, it is possible to adjust these machines (dampers in the ducts) so as to have slightly more air coming in from the outdoors than is going out. This will create a small pressure in your apartment that pushes back on the smoke from the neighbour. If in addition your smoking neighbour puts one in and adjusts it to be slightly negative – taking out more air than in, this will even increase the difference between your apartment and his – which will give him and you both better air –- win-win.
By the way – trying to exhaust out more air from your apartment (bathroom and kitchen fans) will only draw in more smoke from the neighbour's apartment.
Short of ventilation control, all I can recommend is that you put energy efficient gaskets on all the electrical outlets on the neighbour’s side, and caulk behind the floor boards to seal the space between the wall and the floor.
I hope this helps,