Tryckfördelningslåda

The invention relates to a plenum box (1a, 1 b) configured for use in a ventilation system (2) with flowing air in order to be able to quickly regulate flows between the ventilation system (2) and a room. The plenum box (1) comprises a pressure distribution pipe (4) which is disposed in an inlet (3) to the plenum box (1) and which itself comprises a regulating damper (5), and an outlet (6a, 6b). The inlet (3) is configured to have an air flow (7) passing through it. The pressure distribution pipe (4) extends inside the plenum box (1a, 1b) from the inlet (3), and the surface of the pressure distribution pipe (4) has perforations (8) which allow the air flow (7) to pass through them between the inside (9) and outside (10) of the pressure distribution pipe (4). The regulating damper (5) is disposed adjustably in the axial direction (11) inside the pressure distribution pipe (4) whereby the total aperture cross-section (12) of the perforations (8) per unit length varies in the axial direction (11) of the pressure distribution pipe (4).