Sauna is a hot room with temperatures normally varying between 80º-120ºC where the heat is provided by a hot surface (e.g. by an electrically-heated oven). The hot room may also include the space where the oven is located and adjacent bathrooms. <Chapter II-2, part A, regulation 3>.
Source: IMO Resolution MSC.99(73), amendments to the International Convention for the Safety of Life at Sea, 1974, as amended, 5 December 2000, International Maritime Organization. Legislation