T-250 chimney liners are used to narrow down the chimney sections and to adapt them to modern low-temperature oil and gas furnaces.

The system consists of an flexible pipe made of high-alloyed stainless tape, steel type 1.4404, resistant against intercrystalline corrosion and plasma-welded moulders. Such a solution enables the chimney liner to be installed even in a deformed chimney flue.
Acid-resistant flexible pipes are used also in the installation of gas and oil devices as well as for the construction of ventilation systems.