Abstract: An air handling unit for supplying air to a building including an exterior housing forming a chamber and having a longitudinal axis and air inlets and an outlet at opposite ends of the housing. An array of plenum fan units is mounted in the housing between its opposite end sections, this array extending transversely relative to the longitudinal axis. A corresponding array of insulated inlet flow concentrators is arranged adjacent to upstream ends of the plenum fan units. Each concentrator forms a flow passage which tapers towards an inlet opening of its respective fan unit. The flow passage is formed by a perforated metal wall circumferentially encased in sound attenuating material. Interior walls are mounted in the housing to separate the fan units from one another. At least one mechanism is mounted at one end of the compartment for each fan unit formed by the interior walls.