Create a passive Scalar
 

Hello,
I am new and I need a little (or big :D) help with my passive scalar in StarCCM+.
I would like to show the mass concentration of the gas Radon222 in a room. I actually have a Radon Source which is declared as a 'Wall'. It is because the radon is coming out of the water but I only simulate the gas phase.
I created a passive Scalar in the Physics Conditions and calculated the Schmidt Number of Radon.
Then I tried to creat a FieldFunction, but actually I don't know what I should write for the syntax...

I would be so happy if anyone could help me with that :)

Thank you :)
Metti