Both horizontal and vertical ducts are introduced with an air flow direction which depends on the initial and final point when the horizontal ducts are drawn or the initial and final elevation in the case of each vertical duct. Using the “Invert the air flow direction in ducts” tool 
, users can change the direction of flow.
As of the 2018.e version, if the direction of flow indicated by users is incorrect, the program detects this and emits a warning message at the end of the analysis process.
