Qto_DuctSegmentBaseQuantities Base quantities that are common to the definition of all types and occurrences of duct segments. IfcDuctSegment IfcDuctSegment Length Length of the segment, calculated at midpoint of cross-section, equal to the distance between inlet and outlet ports. Q_LENGTH Length GrossCrossSectionArea Area of the cross section, including the duct itself and the interior flow space. Q_AREA Gross Cross Section Area NetCrossSectionArea Area of the cross section of the duct, excluding the interior flow space. Q_AREA Net Cross Section Area OuterSurfaceArea Total area of the extruded surfaces of the duct (not taking into account the end cap areas), normally generated as perimeter * length. Q_AREA Outer Surface Area GrossWeight Weight of the duct segment. Q_WEIGHT Gross Weight