This extension will provide a button on all search results, allowing for one-click detection of smoking policy
AirBnB does not currently allow you to search for non-smoking rooms.
This plugin runs only on AirBnB search results pages, placing a button on the top left of each listing which can be clicked to determine if that listing allows smoking or not. This is not abusive of AirBnB's system in anyway, as you would have to make the exact same requests to their servers to get this information anyway, but with a good bit more effort on your part.
Caveat: When you go to a new page of results via pagination links at the bottom, you will have to refresh the page to get the buttons to show up.