Abstract: A safety device for a pneumatic membrane press with door(s) comprises at least one unit for controlled establishment of a leak, each optionally associated with a cooperating opening/door assembly. Each unit includes an actuator module comprising an opening for receiving a key mounted on the door of the press and an actuating member whose position depends on the presence or not of the key in the opening; and a valve module comprising a sealing member for a circulation duct between an aperture in fluid connection with one or more inflation volume(s) pressurised when the press is pressurised and an aperture opening into the open air, the actuating member allowing the closure of the duct by the sealing member when the key is in the receiving opening and forcing the freeing of the duct when the key is not in the opening.