A sauna (/ˈsɔːnə/ or /ˈsaʊnə/;Finnish pronunciation: [ˈsɑunɑ]), or sudatory, is a small room or building designed as a place to experience dry or wet heat sessions, or an establishment with one or more of these facilities. The steam and high heat make the bathers perspire. Saunas can be divided into two basic types: conventional saunas that warm the air or infrared saunas that warm objects. Infrared saunas may use a variety of materials in their heating area such as charcoal, active carbon fibers, and other materials.
Originally borrowed from the early Proto-Germanic *stakna- whose descendants include English , the word is an ancient Finnish word referring to the traditional Finnish bath and to the bathhouse itself. In Baltic-Finnic languages other than Finnish, sauna does not necessarily mean a building or space built for bathing. It can also mean a small cabin or cottage, such as a cabin for a fisherman.
The Sauna as known in the western world today originates from Finland. There are built-in saunas in almost every house in Finland. The oldest known saunas in Finland were made from pits dug in a slope in the ground and primarily used as dwellings in winter. The sauna featured a fireplace where stones were heated to a high temperature. Water was thrown on the hot stones to produce steam and to give a sensation of increased heat. This would raise the apparent temperature so high that people could take off their clothes. The first Finnish saunas are what nowadays are called savusaunas, or smoke saunas. These differed from present-day saunas in that they were heated by heating a pile of rocks called kiuas by burning large amounts of wood about 6 to 8 hours, and then letting the smoke out before enjoying the löyly, or sauna heat. A properly heated "savusauna" gives heat up to 12 hours.