@Margareta14 I'm sorry you had this experience. The protocol for a guest when they arrive to a listing to find something not as expected, whether it's smoke smell, an uncleaned place, or whatever, is to first notify the host, so they have an opportunity to correct it, if possible. If the host is non-responsive, or can't do anything about it, and doesn't offer to refund you in full if it's necessary for you to leave, then you contact Airbnb, explain the situation, and ask them to cancel the rest of your reservation and locate a different place for you to stay. That way you'll automatically be refunded, according to the host's cancellation policy, or if it's a matter that Airbnb considers bad enough, you might be fully refunded.
The host was probably not misrepresenting the place as far as no-smoking. There are guests who simply ignore house rules, so the previous guest may have been one of those. If it's an off-site host who employs a cleaner, rather than cleaning and inspecting the unit themselves, the host may not have even realized it if the cleaner didn't report smoke smell. That's why it's important to let the host know first if something is wrong- they may not be able to do anything about the smell for your stay, but if they haven't yet reviewed the previous guest, they can mark them down for not following huse rules and state that in the written review. That way, guests who do things like this will have it show on their profile, and future hosts will be wary about accepting their bookings. And the host won't be surprised and wonder why you left.
At this point, if you didn't officially cancel this stay, you should do so now, if you had more days left on the reservation and you can contact Airbnb to explain the situation.