Double Hull Flues are used in boilers working with solid, liquid and gas fuels. These flues work with the help of the heat and the difference in the pressure...

Single Hull Flues are used in combi boilers, cascading systems or central heating boiler connections. Single Hull Flues can be used with any type of fuels. T...

They are the industrial kind of chimney systems that are used in factories. They are not appropriate for daily use. ...