Conor Mc Carry

I'm trying to find how much DPM concentration passes through a vent in a study to reduce DPM concentration with various vent designs. I am tring to do a grid independance study, but my mean value for DPM concentration changes so much between each mesh. Im using a 3D domain with meshs with cells of, 128k, 234k, 542k, 771k, 949k. Do I have to use a steady model for the mesh independance study instead of unsteady?