Smoke sauna (Finnish savusauna) is one of the earliest forms of the sauna.
It is simply a room containing a pile of rocks, but without a chimney.

A fire is lit directly under the rocks and after a while the fire is extinguished.
The heat retained in the rocks, and the earlier fire, becomes the main source for heating the sauna. Following this process, the ashes and embers are removed from the hearth, the benches and floor are cleaned, and the room is allowed to air out and freshen for a period of time. The smoke deposits a layer of soot on every surface, so if the benches and back-rests can be removed while the fire is alight the amount of cleaning necessary is reduced.
Depending on size of the stove and the airing time, the temperature may be low, about 60 °C (140 °F), while the humidity is relatively high.

The tradition almost died out, but was revived by enthusiasts in the 1980s. These are still used in present-day Finland by some enthusiasts, but usually only on special occasions such as Christmas, New Year's, Easter, and juhannus (Midsummer)