The second option is more common, and is an independent double -walled steel chimney. The internal and outer pipes in it are separated by a layer of non -combustible heat -resistant heat insulator (usually basalt fiber), which avoids excessive overheating of the outer surface of the chimney. A similar type of pipes differs mainly by the thickness of the inner layer-fluctuating within 30-100 mm, depending on the types of roofs, installation sites, climatic conditions, humidity of the room, etc. D. The maximum layer of basalt wool is used in chimneys for a bathhouse, where heat losses are most critical.
