The systems are used for exhausting flue gases from condensing and low-temperature boilers with the highest flue gas temperature at the appliance smoke outlet of 120°C. It is designed mainly for positive pressure and high pressure flue gas paths. They can also be used for natural draught chimneys. It is not intended for flue gas ducts where soot can burn out. It is suitable for chimneys that are planned to be operated in wet operation mode and applicable for flue gas flue from appliances burning gaseous fuels or natural gas (L,H) and liquid fuels (LTO with sulphur content up to 0,2% kerosene).