As part of the Green Deal, the EU Commission is calling for climate neutrality for the entire European Union by 2050. One way to achieve this goal in aluminum casthouses is to use hydrogen as a fuel instead of natural gas. The switch from fossil energy sources to H2 in the melting and casting furnaces would be associated with a significant reduction in the CO2 footprint. In the opposite direction, however, firing hydrogen results in a significant increase in the water vapor concentration in the off-gas atmosphere. Until now, it has been unexplored how such a change affects dross formation. In this work, therefore, an investigation of the oxidation behaviour of various aluminium alloy melts under different simulated furnace atmospheres with water vapor contents between 13 vol.-% and 89 vol.-% is carried out. For this purpose, samples with a mass of around 60 g are melted and held in an electrically heated tilting crucible furnace at 850 °C under various test atmospheres, which are based on industrial furnaces in terms of their composition. Essentially, a comparison is made between the exhaust gas atmospheres of the combustion reactions natural gas + air, hydrogen + air and hydrogen + oxygen. The characterization is carried out by gravimetric evaluations, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The results confirm a relationship between the composition of the furnace atmosphere and the oxidation behaviour of Al alloys. There is a tendency for oxidation to decrease with increasing H2O content. The SEM analyses carried out suggest that increased water vapor concentrations in the atmosphere lead to a stabilization of the first formed MgO layer. Subsequently, this protects the melt from additional oxidation. Besides, no further oxidation-inhibiting effect is shown in the presence of carbon dioxide. It can therefore be assumed that increased dross formation in the furnaces is not to be expected with industrial use of H2 instead of CH4 as fuel.