Yeah, our first place was so bad in places from the previous owner we had to replace electrical outlets because they were gummed up with tar and nicotine film. Even after all that you’d get a whiff of that smell when you turned the AC or heat on for the first time in a season. That didn’t go away until after we replaced the main duct. We did that because it was leaking pretty badly and heating/cooling a room no one was ever using.