Abstract
The use of alarms in process control is a complex affair, because alarms can have many different functions over and above that of alerting the operator to a new event. Alarms are potentially a rich source of information that can be used in all phases of responding to a disturbance and should therefore be considered as an aspect of the general process information. From the point of view of cognitive systems engineering, alarms provide information that enables the operators to maintain control of the process and to be proactive as well as reactive. An important issue is the time and effort needed to evaluate events and new information (time to evaluate: TE) and the time and effort needed to select an appropriate response or line of action (time to select: TS). The former (TE) can be supported by more effective presentation of information, specifically a more comprehensive presentation of alarms. The latter (TS) can be supported by various kinds of computerized support, ranging from planning systems to adaptive and computerized procedures.