The double-walled chimneys are designed for boilers burning gaseous fuel. Such boilers include two pipes - outer pipe (housing) and inner pipe (i nterior). The layer of noncombustible wool (basalt) is located inside of such pipe. I t has thickness 30-35mm and withstands high-temperature mode. This characteristics allow maximum conserving of gas temperature that facilitates formation of smoke draft and avoids formation of excess condensate. Currently heat insulated stainless steel chimneys enjoy strong demand, as, besides high performance, they have excellent fire safety permitting their installation in saunas and timber houses. However, fire safety rules should be observed even with installed heat insulated chimney. The other advantages are lightness and compact sizes of elements, and so the base for structural reliability is not necessary. Wall fastening and lightweight stretching rops are usually used that significantly simplifies installation of the system.