Ethos EconAir 4.2m Flue Kit for Freestanding Wood FiresEthos EconAir 4. 2m Flue Kit The Ethos EconAir 4. 2m Flue Kit has been specifically designed for Ethos freestanding wood fires and forms a critical part of the unique Ethos heating system. Unlike conventional wood fire flues, the patented EconAir design draws combustion air from outside the building and pre heats it before it enters the firebox. This innovative system improves combustion efficiency, reduces emissions, eliminates cold draughts, and