A containment system for laterally containing a liquid metal material or liquid metal alloy at an open side end of a passage defined between two casting members, the system including a pneumatic device ending with a hollow end element adapted to be arranged close to the open side end of the passage, wherein the hollow end element defines a chamber therein, wherein the pneumatic device is adapted to feed a compressed aeriform substance into the chamber, and wherein the hollow end element is provided with at least one blowing face for blowing the compressed aeriform substance from the chamber towards a side containment zone for the liquid metal.