I agree with @Lynick4442. It will be difficult to collect a deposit for the smell, because AirBnB requires proof of damage through pictures. You would have to submit receipts for the damage, so the most you would probably get is get money for the extra cleaning supplies. I completely understand your frustration, as I have the same strict no smoking rules (and I even state no smokers allowed as I get sick even with the smell of smoke that lingers on their clothes and gets transferred to the bedding). If you have no smoking in your rules and they are still doing it, you can have AirBnB help you relocate them for rule-breaking, but I don’t know what kind of proof you’d have to have for that either. If you end up finishing the reservation and if the room smells when they leave, I would suggest putting out bowls of vinegar, sprinkling baking soda on the mattress, carpet, and any other fabric areas, and spraying Ozium spray to get rid of any odor.