Dual plenum for air distribution

A dual plenum for air distribution comprising:

• a first chamber (1) and a second chamber (2) sharing at least one common wall (14) and further sharing an air outlet (10, 11) having diffusers (12, 13) in an air passage area (S1, S2) configured to direct air within an enclosure in general of a building.
• an air-feed device configured to selectively introduce, through an air supply conduit (9), pressurized air from an air supply source (8) to the first chamber (1) or to both the first chamber and the second chamber (2) in response to a supplied pressurized air flow rate;
• wherein said first chamber (1) is connected to one first air passage area (S1) of said air outlet (10), and said second chamber (2) is connected to a second air passage area (S2) of said air outlet (11),
• characterized in that the pressurized air supply conduit (9) is connected only to the first chamber (1);
• the common wall (14), includes an air passage regulating device (7) configured to selectively communicate the second chamber (2) to the first chamber (1) in response to an air pressure level in the first chamber (1) caused by the supplied pressurized air flow rate.