Thanks for your reply, Rob.

Would you please elaborate a little more how increasing the first cell height will result in the model accounting for interception too? You once said that particle trap on the walls won't be examined unless the particle is in the near-wall cell. However, even if my near-wall cell's height is 10 microns and I'm studying a 5 micron particle, the particle still has to hit the wall to be counted as trapped and it won't be trapped if it comes to a let's say 1 micron particle center to wall distance. (Or will it? Please correct me if I'm wrong). If the model doesn't trap the particles at the wall distances below the particle radius, there is a chance that the particle that should've been marked as trapped would flee away from the wire and it will cause an underprediction in the filter efficiency. 

That would be great if you could please send me the relevant fluent manual documents in this regard as I couldn't find them.

Thank you