What is the difference between an open and a closed system?
Gas fires with an open combustion system take the oxygen that is required to burn the gas from the room in which the device is placed or possibly through a separate air supply. The flue gases are removed through a separate flue duct.
In a closed system the device takes the air that is required for the combustion directly from the outside and removes the flue gases through the same, concentric duct. This means that the flue can simply be installed through the wall or roof in many cases. The introduction of this system has made traditional chimneys redundant. Moreover, it increases the flexibility in relation to the exact location of the fire.
As a closed system draws oxygen from outside air and therefore not from the room where the fire is located the system is ideal for modern, well insulated and mechanically ventilated homes. The fact that traditional chimneys are no longer required and that it is simple to install a flue through a wall gives an increasing number of people the solution for the location of a fire