in:Flux streamlines provide a way for users to study the flow in and around CAD objects in a facility. A key factor of streamlines for in:Flux is the 'seed point' which notifies in:Flux for where the lines should be within the domain - every line in the streamline will pass through the seed points. This concept is important to understand for creating unique streamline visuals.
The streamlines are useful to give a generally feel for the flow, but if you are looking at the ventilation in a particular area it is advised that vectors be used.