The expansion of an existing shelter used for hydrogen and oxygen storage, located within the Sapio Oxygen Production Plant S.r.l., is characterized by a structure with beam profiles, arched windows and pillars in blue painted steel. The perimeter walls are made of honeycomb blocks and the cover in sandwich panels of corrugated metal sheet. Special attention was paid, both on the design and on the realization phase, to the assembly of steel structure, due to the presence of explosive materials: there were used bolted joints so to avoid welding in operation.