What B-EM Is
A BACnet device profile is a standardized capability level: a checklist of things a device must be able to do before it can wear the label. B-EM (BACnet Elevator Monitor) is defined in Annex L of ANSI/ASHRAE 135-2024 (clause L.13.3) as a read-only view of an elevator or escalator group: it reports status and generates events, but it does not accept commands to the equipment.
The checklist items are BACnet Interoperability Building Blocks (BIBBs). B-EM is a B-role device with no write requirement, the elevator equivalent of a monitoring-only controller. A device documents its claim in its PICS (Protocol Implementation Conformance Statement); to verify a claim, ask for the PICS and check the profile line.
Where It’s Used
B-EM fits a device that surfaces elevator or escalator status to a building system without controlling the equipment.
- Elevator status to the BMS. Reporting car position, direction, and fault status for display at the head end (the central BMS server).
- Escalator monitoring. Surfacing run and fault states of escalators as BACnet objects.
- Read-only lift integration. Exposing an elevator controller’s status where the building system watches but does not command.
Required Services
The table below is the exhaustive service set required by the B-EM BIBBs. Initiates means the device sends the request or notification; Executes means the device receives and acts on it (responding, for confirmed services). BIBB codes encode the same split: a -A BIBB is the initiating side, a -B BIBB the executing side. A - means the profile does not require that direction; a device may still support it.
| Capability area | Service | Required by BIBB | Initiates | Executes |
|---|---|---|---|---|
| Data sharing | ReadProperty | DS-RP-B | - | Yes |
| Data sharing | ReadPropertyMultiple | DS-RPM-B | - | Yes |
| Data sharing | SubscribeCOV | DS-COV-B | - | Yes |
| Data sharing | ConfirmedCOVNotification | DS-COV-B | Yes | - |
| Data sharing | UnconfirmedCOVNotification | DS-COV-B | Yes | - |
| Data sharing | SubscribeCOVPropertyMultiple | DS-COVM-B | - | Yes |
| Data sharing | ConfirmedCOVNotificationMultiple | DS-COVM-B | Yes | - |
| Data sharing | UnconfirmedCOVNotificationMultiple | DS-COVM-B | Yes | - |
| Alarm and event management | ConfirmedEventNotification | AE-N-I-B | Yes | - |
| Alarm and event management | UnconfirmedEventNotification | AE-N-I-B | Yes | - |
| Alarm and event management | AcknowledgeAlarm | AE-ACK-B | - | Yes |
| Alarm and event management | GetEventInformation | AE-INFO-B | - | Yes |
| Device and network management | Who-Is | DM-DDB-B | - | Yes |
| Device and network management | I-Am | DM-DDB-B | Yes | - |
| Device and network management | Who-Has | DM-DOB-B | - | Yes |
| Device and network management | I-Have | DM-DOB-B | Yes | - |
| Device and network management | DeviceCommunicationControl | DM-DCC-B | - | Yes |
The elevator status is modeled as hosted objects. The device presents its equipment through Lift and Escalator objects, which carry the car and step status the profile reports.
Related Profiles
| Profile | How it differs from B-EM |
|---|---|
| B-EC | Elevator Controller: adds write access and time synchronization; commands as well as monitors |
| B-AEC | Advanced Elevator Controller: adds an event log, internal scheduling, and backup and restore |
| B-EWS | Elevator Workstation: the operator-side profile that displays these devices |
What Chipkin Provides
The CAS BACnet Stack implements the BIBB set the B-EM profile requires, including the Lift and Escalator object model and event generation. Talk to us about building or integrating a B-EM device on the stack.