[EN 16798-3:2017, 3.3]:volume designed for human occupancy specified by horizontal and vertical planes.
[EN 12792:2003, 273]:volume of air, which is confined to horizontal and vertical planes. The vertical planes are usually parallel with the walls of the room. Typical definitions for the occupied zone are given in the following table. Except when agreed otherwise the default values shall be applied.NOTE The occupied zone in a room is that space in which persons normally reside and where the requirements of the indoor environment shall be satisfied.

[ISO 16814:2008, 3.28]: area designed for occupancy that is dependent on the geometry and the use of the room and specified case by case. NOTE Usually used only for areas designed for human occupancy and defined as a volume of air that is confined by horizontal and vertical planes. The vertical planes are usually parallel with the walls of the room.