It really depends on what the smell is. New air fryers that are being used for the first time can smell like burned plastic. This is pretty normal and nothing to worry about. It should subside over a few uses.
On the other hand, if you've got a stinky air fryer from regular use, try mixing equal parts of lemon juice and distilled vinegar in the aforementioned oven-safe bowl, placing it in the air fryer, and setting it on high for two minutes. Be super careful when taking the crockery out!