The seat and backrest are each composed of a block of moulded polyurethane foam with an internal metal structure. Upholstery is joined to the foam using the INTEGRAL FORM system, without seams or stitching. A 5-mm TS System fire barrier incorporated between the foam and upholstery on both the seat and backrest prevents fire from reaching the foam, delaying the spread of flames and emission of toxic gases in the event of a fire. Backrest padding is anatomically contoured, with lateral support and a head pad, and vertical and horizontal grooves in the head pad area. Seat padding has a smooth anatomical form and is free of grooves of any kind in order to prevent dirt from accumulating on the surface. The IF-727 polypropylene pieces used on the seat and backrest are fully washable and protect the upholstery on back surfaces. The seat is fixed in the open position. Each chair is mounted on a central pedestal. The pedestal is attached to an internal bridge that links the individual units to form rows that are completely rigid and stable. Pedestals are made of tubular steel finished in black or grey epoxy paint. Chairs are fixed to the floor using expansion bolts. The base of the pedestal can be adjusted to the floor slope. Rows are formed by interconnected backrests. This system ensures complete rigidity and stability, thus reinforcing floor fixation. Chair arms are made of polyurethane foam with an internal metal structure and a cupholder that is integrated in the armrest in a compact manner. Both the seat and the backrest incorporate the TX acoustic system, consisting of acoustic perforations on the back and bottom covers, a design feature that ensures an excellent acoustic response. Optionally, the upper rear face of the backrest can incorporate an upholstered section. The seat can be fully upholstered without losing any of its acoustic properties. An HR version can also be used for the backrest. In this case, the headrest is integrated in the backrest rather than being added on as a separate element. The ergonomic advantage of this type of headrest is that it is a natural prolongation of the backrest, not an add-on accessory element.