Poltergeist

My first thought would be an air quality sensor but I’m not sure how sensitive they would be to food smells. I’ve never used one but there are plenty of examples online.

A fallback would be a timer, if you know when your neighbor usually cooks, you could turn your fan on during those times with some buffer.

About 30 pins could be used for various inputs depending on the board. Here is a good reference. https://randomnerdtutorials.com/esp32-pinout-reference-gpios/