The "U.D.M." decontamination unit it is substantially derived from a three-stage personnel decontamination unit. In fact, all the external structure is reused, replacing the two panels with two open panels, on one of which the flap is installed in polyethylene and anodised steel, instead of the door. This allows the operator within the "dirty" zone to enter the contaminated bags leaving the contaminated area, in a tank filled with water and encapsulating. The tank is equipped with an overflow hole and the tank drain is connected directly to a water filtration unit equipped with suitable asbestos filters.