According to Regulation (EU) 1253/2014, the definitions for local and central demand control are as follows (Annex I, part 1):
(24) ‘central demand control’ means a demand control of a ducted ventilation unit that continuously regulates the fan speed(s) and flow rate based on one sensor for the whole ventilated building or part of the building at central level
(25) ‘local demand control’ means a demand control for a ventilation unit that continuously regulates the fan speed(s) and flow rates based on more than one sensor for a ducted ventilation unit or one sensor for a non-ducted unit
In other words, Regulation (EU)1253/2014 states that the difference between local demand and central demand is determined by both the number of sensors and the difference in the flow rate (or rates) being controlled.
Therefore, local demand control for ducted BVUs refers to at least two sensors placed locally in zones/rooms, or in the airstream to/from the rooms/zones where the airflow to the individual rooms/zones is regulated according to the local demands measured by the sensors in/to/from the room/zone. The local flow to/from the rooms/zones is usually regulated by dampers if it is ducted centralised ventilation, and if it is local ventilation by a device that is part of the total unit. The total flow provided by the fans in the unit is operated according to the sum of the individual local demands, usually determined by pressure sensor(s).
For single locally-placed non-ducted units, Regulation (EU)1253/2014 only requires, for the local demand control, one sensor and the regulation of the entire flow of the unit as it is placed locally in the room/ zone.
Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.