A mobile plant designed for aspiration, treatment, suppression and depuration of fumes and/or dust and/or gaseous mixtures coming from processing of metals or other materials, the mobile plant comprising: - a covering of the processing zone suitable to prevent the dispersion into the atmosphere of the fumes and/or dust and/or gaseous mixtures produced during the processing; and - a plant for aspiration and treatment of the fumes and/or dust and/or gaseous mixtures present in the covering, - a filtration system acting in conjunction with the covering and the aspiration and treatment plant, characterised in that the covering comprises a hood disassembleable and movable on wheels slidably engaged in tracks, associated with a frame, between an operating position above a work area and a standby position outside the work area; the frame being restable on or fixable to the ground under operational conditions of the plant, the work area being comprised between the tracks; the hood being tunnel-shaped and comprising: - a front wall integral with the hood and which can be at least partially opened, the front wall and the hood being slidable from and/or to the work area; - a rear wall integral with a frame, which is restable on or fixable to the ground under operational conditions of the plant, in such a way as to remain fixed during movement of the hood, the rear wall having a radius less than the radius of the tunnel-shaped hood in such a way that the tunnel-shaped hood complete with a front wall, can slide along the tracks and above the rear part; - a plurality of modules, each having a tunnel shape and being mutually attachable and lockable with each other, and comprising at least two frames, formed by a central half arch hinged to respective lateral half arches (16, 17, 18); each of the half arches (16, 17, 18) is made integral with portions of thin and resistant material suitable for forming the covering of the module. - a covering of the processing zone suitable to prevent the dispersion into the atmosphere of the fumes and/or dust and/or gaseous mixtures produced during the processing; and - a plant for aspiration and treatment of the fumes and/or dust and/or gaseous mixtures present in the covering, - a filtration system acting in conjunction with the covering and the aspiration and treatment plant, - a front wall integral with the hood and which can be at least partially opened, the front wall and the hood being slidable from and/or to the work area; - a rear wall integral with a frame, which is restable on or fixable to the ground under operational conditions of the plant, in such a way as to remain fixed during movement of the hood, the rear wall having a radius less than the radius of the tunnel-shaped hood in such a way that the tunnel-shaped hood complete with a front wall, can slide along the tracks and above the rear part; - a plurality of modules, each having a tunnel shape and being mutually attachable and lockable with each other, and comprising at least two frames, formed by a central half arch hinged to respective lateral half arches (16, 17, 18); each of the half arches (16, 17, 18) is made integral with portions of thin and resistant material suitable for forming the covering of the module.