Hi @march, thanks for posting on the forum and welcome to the SimScale Community 
I think your best shot modelling this problem with SimScale is to use Passive Scalars. Passive scalars are basically components such as pollutants, immiscible gases, etc. which are transported by the flow (don’t alter it’s properties). This tutorial has a nice example on how to use this approach to model such a case.
Please note that you don’t necessarily need to model them as advanced concepts, but also to insert them as values coming out of velocity inlets.
Cheers
Igor