A zone is a group of spaces, partial spaces or other zones. Zone structures may not be hierarchical (in contrary to the spatial structure of a project - see IfcSpatialStructureElement), i.e. one individual IfcSpace may be associated with zero, one, or several IfcZone's. IfcSpace's are grouped into an IfcZone by using the objectified relationship IfcRelAssignsToGroup as specified at the supertype IfcGroup. 

The Property Sets for Objects concept template applies to this entity under Pset_ZoneCommonname as shown in table below:

The concept also applies to this entity under the Pset_ZoneCommonname:

An IfcZone is a spatial system under which individual IfcSpace's (and other IfcZone's) are grouped. In contrary to the IfcSpatialZone entity, IfcZone is a mere grouping, it can not define an own geometric representation and placement. Therefore it cannot be used for spatial zones having a different shape and size compared to the shape and size of aggregated spaces. 

In case of a zone denoting a (fire) compartment, the following types should be used, if applicable, as values of the ObjectType attribute:

• 'FireCompartment': a zone of spaces, collected to represent a single fire compartment.
• 'ElevatorShaft': a collection of spaces within an elevator, potentially going through many storeys.
• 'RisingDuct': A collection of vertical airspaces.
• 'RunningDuct': A collection of horizontal airspaces.

changes 

• IFC4 changes: The entity is now subtyped from IfcSystem (not its supertype IfcGroup) with upward compatibility for file-based exchange.