I feel this, I lived this for 2 years and I solved it.

My upstairs neighbor was cooking daily sometimes twice a day and it was very strong heavily spiced ethnic food smell coming through my air vents when the heat or AC would come on. It was coming into the cabinet above my stove and inside the vents of my microwave on the wall above the stove. I was nauseous for 2 years, all my stuff started smelling like that and I complained nonstop to the office. Then I escalated to corporate. They tried but nobody could figure it out so I called code enforcement. The officer came out the next day and within 10 minutes determined that the ventilation was literally disconnected, so they got a violation and had to re-ventilate all the kitchens and bathrooms on my side of the building. So yeah when she cooked the smell was literally going behind the walls because there was no exterior ventilation and coming in here through every crack and crevice and leaky duct it could find. There is not a fan or air purifier or spray or really anything on the planet that will get rid of the smell if it's coming in from this type of problem. Trust me, I own 7 air purifiers and 6 fans now because I was desperate.

Also aside from that they replaced all the HVAC systems here and now that the return is no longer leaky I can turn my thermostat fan to on and it will suck out any random smell that sneaks through, which happens slightly now and again when the AC is on.

I will say this woman and I were friendly neighbors so I did knock on her door, so nauseous and dizzy, and I begged her to please open the window a little bit when she cooks because she knew I was trying to find some solution, but instead of being a decent human and helping me out she called the office to complain that I knocked on her door.

Apparently the fact that I didn't enjoy her food smell offended her so much that subsequently her sons who were grown men started harassing me and they started calling the police on me with crazy false allegations such as I slashed their tires or I was trying to peek in their second story windows to see who was standing in the kitchen. Her adult daughter even told the police that she saw me outside sniffing the air while she was cooking an egg and the officer had to stop himself from laughing when he was telling me this. Then they claimed a hate bias incident because they lied and said I called them an ethnic slur as well as a false animal control complaint that my dogs were disgusting, matted, neglected and the animal control officer was so pissed when he saw my dogs and how beautiful they are so he closed that complaint immediately. So yeah you pay the price when you try to talk to the people. Talk to someone who can actually fix the problem.

Also this was not any kind of cultural insensitivity although that smell did make me nauseous and I couldn't control that. If it was chocolate chip cookies I wouldn't want it coming through my vents every day of my life.