This European Standard sets the requirements for functional safety for HBES/BACS products and systems, a multi-application bus system where the functions are decentralised, distributed and linked through a common communication process. The requirements may also apply to the distributed functions of any equipment connected in a home or building control system if no specific functional safety standard exists for this equipment or system. The functional safety requirements of this European Standard apply together with the relevant product standard for the device if any. This European Standard is part of the EN 50491 series of standards. This European Standard does not provide functional safety requirements for safety-related systems.