The application relates to apparatus capable of easily mounting an indicator to a device for verifying a sterilizing effect when a sterilizing process is performed. An installation apparatus is disclosed for positioning a sterilization verifying device in a sterilizing chamber having a sterilizing chamber door, said sterilization verifying device comprising a containing chamber for containing an indicator, the containing chamber having an opening for receiving an indicator into the chamber and connected to an introduction tube for introducing a sterilizing gas into the containing chamber, the installation apparatus comprising arrangement means configured to, in a case that the sterilizing chamber door is closed, position the opening of the containing chamber with respect to an inner wall of the sterilizing chamber door, such that the inner wall and the opening are brought into contact with each other thereby sealing the containing chamber against the inner wall.
