A Short Account of Fumigating, Hot Air, and Vapour Baths (1837)
Originating from the Roman bath or a Turkish bath, the vapour bath was essentially a sauna or steam bath that in the late Regency era into the Victorian era was created to be very portable to treat a variety of ailments.
I was able to find several publications from the Regency era citing the benefits of the vapor bath particularly for gout and rheumatism, but also for arthritis and congestion. Some papers also made other claims about the healing properties of the dry pump or vapour bath.
The most common vapour bath in the UK during the Regency was a solitary bath, rather than a communal bath, to be employed either in a specially built room or with apparatus as described above.