Thank you, Rob. When checking Reports>Discrete Phase Sources>DPM Mass Source (Sum) the given value is 0 kg/s. When checking this variable for DPM “species” Source, there is an output (negative, leaving the fluid). Do you have any idea why this first variable hasn’t the same value as the second (only one species is exchanged)? How can I fix that the source term to the conservation equation is the same as the one for “species”?