This entity is a description of a panel within a door or window (as fillers for opening) which allows for air flow. It is given by its properties (IfcPermeableCoveringProperties). A permeable covering is a casement, such as a component, fixed or opening, consisting essentially of a frame and the infilling. The infilling is normally a grill, a louver or a screen. The way of operation is defined in the operation type. 

The IfcPermeableCoveringProperties are included in the list of properties (HasPropertySets) of the IfcWindowStyle or the IfcDoorStyle. More information about the permeable covering can be included in the same list of the window or door style using the IfcPropertySet for dynamic extensions. This particularly applies for additional properties for the various operation types.