An Alarm Summary entry is the data structure returned by the Get Alarm Summary confirmed service. It gives a client a compact, point-in-time list of every object inside a device that is currently in an alarm or fault condition and that the client is permitted to observe.

Each summary contains three pieces of information: the Object Identifier of the alarming object, its current Event State (which may be FAULT or one of the alarm states such as HIGH_LIMIT or LIFE_SAFETY_ALARM), and the Acknowledged Transitions bit string. The acknowledged transitions bits are crucial for operator interfaces because they indicate which state changes still require human acknowledgment before the alarm can be considered fully cleared from the operator's perspective.

Although Get Alarm Summary is one of the older summary services in BACnet, it is still widely supported for backward compatibility. Newer implementations are encouraged to use the more capable Get Event Information service, which returns timestamps, notification class, and other context. The Alarm Summary structure itself remains useful whenever a very small encoding is required.