It pull in outside air, yes, but things are more dynamic than that. Most likely you don't have perfect seals on all your windows, walls, doors, pipes, fans etc.

It pull in outside air, yes, but things are more dynamic than that. Most likely you don't have perfect seals on all your windows, walls, doors, pipes, fans etc. Secondly, the air from cooking is generally very bad, especially if you're using nonstick surfaces or using much of anything with oil. It's probably better to trade it for smokey air outside.