Concentration C2H4 as trecer gas
 

I would like to simulate the development of Concentration C2H4 as trecer gasin a building from point source by using Fluent in order to validate wind tunnel results. Unfortunately, I can't find any function in Fluent to simulate concentration . Can anyone tell me if there is any function to do this in Fluent and what are they ?

It looks like I could simply put a (constant) source without any chemical reaction to simulate concentration, Could you please give me any suggestion or comment on this ?

Thanks in advanc. MFYE