Gas mixer, that comprises one or more feed modules each one of these connectable to the supply sources of a first and of a second inlet gas, wherein each feed module is designed to supply a feed gas selectable among the first and the second inlet gas towards a flow regulator, wherein the feed module comprises: • selecting body that receives the first and the second inlet gas coming from a first and from a second inlet channel respectively, and that has an internal circuit designed to carry the selected feed gas towards an outlet channel connectable to the flow regulator; • a first solenoid valve joined to the selecting body, connected to the internal circuit to open or close the path of the first inlet gas towards the outlet channel; and • a second solenoid valve joined to the selecting body, connected to the internal circuit to open or close the path of the second inlet gas towards the outlet channel; said mixer characterized in that it comprises a homogenizing module comprising: • an inlet block that has: - a mixture cavity with a plurality of inlet holes facing each other and one outlet hole oriented perpendicular to the inlet holes; and - a plurality of inlet fittings each one connected to one of the inlet holes, wherein said fittings are designed to receive the feed gas coming from each flow regulator and allow its turbulent mixing inside the cavity; • a first mixture deposit that connects to the outlet hole and that is designed to contain in its interior the mixture of feed gases coming from the inlet block; and • an outlet block of the mixture of gases coming from the first deposit that has an outlet fitting. • selecting body that receives the first and the second inlet gas coming from a first and from a second inlet channel respectively, and that has an internal circuit designed to carry the selected feed gas towards an outlet channel connectable to the flow regulator; • a first solenoid valve joined to the selecting body, connected to the internal circuit to open or close the path of the first inlet gas towards the outlet channel; and • a second solenoid valve joined to the selecting body, connected to the internal circuit to open or close the path of the second inlet gas towards the outlet channel; said mixer characterized in that it comprises a homogenizing module comprising: • an inlet block that has: - a mixture cavity with a plurality of inlet holes facing each other and one outlet hole oriented perpendicular to the inlet holes; and - a plurality of inlet fittings each one connected to one of the inlet holes, wherein said fittings are designed to receive the feed gas coming from each flow regulator and allow its turbulent mixing inside the cavity; - a mixture cavity with a plurality of inlet holes facing each other and one outlet hole oriented perpendicular to the inlet holes; and - a plurality of inlet fittings each one connected to one of the inlet holes, wherein said fittings are designed to receive the feed gas coming from each flow regulator and allow its turbulent mixing inside the cavity; • a first mixture deposit that connects to the outlet hole and that is designed to contain in its interior the mixture of feed gases coming from the inlet block; and • an outlet block of the mixture of gases coming from the first deposit that has an outlet fitting.