Abstract: A tight insulator (10) is equipped with a ventilation circuit having an intake pipe (14) and an exhaust pipe (16), in such a way that the internal insulator volume (12 ) is under an overpressure with respect to the outside. In order to rapidly discharge objects from volume (12), a discharge tube (28) is provided, which is closed by a door (34) and to which is connected the exhaust pipe (16).