Modelling human alarm initiated activities: implications for alarm system design

An alarm handling sequence can be described as consisting of a number of generic activity stages. These generic activities have been assembled into an analysis of alarm handling (Stanton et al., 1992; Stanton, 1994) as shown in the present paper. The analysis distinguishes between routine events involving alarms and critical events involving alarms. Although the two type of events have most activities in common, critical events are distinctive by virtue of an investigative phase. It is proposed that the notion of AIA (alarm initiated activity) is used to describe the collective of the stages in alarm event handling. The term 'activities' is used to refer to the ensuing behaviours triggered by the presence of alarms. It is posited that these activities would not have been triggered without the alarm being present, thus alarm initiated activities. The AIAs are linked to other supervisory control activities which can be typified as continuous tasks (such as visual scanning of instruments and fine tuning of plant variables in response to minor variations in plant) and discrete tasks (such as putting plant into service and taking plant out of service).