Disclosed is a method for monitoring installations by means of a field bus which is used in process automation technology and via which several field devices communicate with a process control unit and an installation monitoring unit. Said method comprises the following steps: the regular data traffic on the field bus which is used for controlling processes is monitored by the installation monitoring unit; the telegrams of the regular data traffic are checked for data indicating a diagnostic event in one of the field devices; and the installation monitoring unit requests additional diagnosticdata from the respective field device if a telegram is identified that contains an indication of a diagnostic event.