In EAF operation, there is a large amount of air ingress: around 30 000 Nm³ in a standard EAF of 150 ton steel with a heat duration of 1 hour. This air is at ambient temperature, the N₂ content and the non-reactive oxygen are heated in the furnace and exit with the fumes at high temperature, resulting in significant thermal losses. Airtight furnace has been assessed to be of potential benefits. With airtight operations, about 80% of the savings can be attributed to a reduction of energy losses in the fumes. The remaining 20% are accounted for by reduced thermal losses due to a reduced elaboration time.