We are living in a house that was remodeled after purchasing from heavy smokers. Our source tell us that they used to smoke packs of cigarettes a day. Then, it was purchased and remodeled. 5 years later we moved in, and you can still smell something, specially when is humid our rainy outside. My whole thought is that they probably painted on top of the tar and maybe they didn't wipe the walls or wash before painting. could that be the issue? I know it sounds crazy, but could we sand all the walls to get rid of the old paint/tar? and then prime and kills/ paint again? Thank you for your time.
Trying to sand off paint from drywall just isn't something that's feasible. Your best bet is to use a shellac based primer or other primer made specifically to block odors. A primer that I'm familiar with and have used with good results is Zinsser BIN primer. I'm sure other manufactures make similar products.
The shellac base means the primer dries super fast (like 15-20 minutes), and because of that, you should plan on treating any brushes or rollers you use as disposable. Cleaning is difficult and pretty hard to do correctly.
I've used it to seal in smoke smells on a ceiling and even an area on a floor and wall where an animal died.