4.1.3-3 Filtered Alarms

Alarm filtering should only be employed where alarm messages have no current operational significance to the crew's monitoring, diagnosis, decision making, procedure execution, and alarm response activities.

Additional Information:
As the term is used here, filtered (as contrasted with suppressed) alarm messages are eliminated and are not available to the operators. Research has indicated that operators prefer to have information available to them to support verification and decision-making activities. Thus, only alarms that can be demonstrated to have no operational significance to operators should be filtered. This includes alarm messages that are irrelevant within the context of the current plant mode or the configuration of the associated plant system. For example, alarm messages that indicate that a pump discharge pressure is low after the fluid system has been removed from service should be filtered. Alarms that are considered redundant or lower priority should be suppressed (where operators can retrieve them) rather than filtered.