You will want to go into the emitter’s properties.. click on the particle type (in this case it says “Dust”)…then go into “Size Over Life”. You will notice that it is slowly rising from 0 to 200 with numerous keyframes (creating a curve on the graph as it rises) to give it a smoother increase in size. What you want to do, to make it appear as if you are moving Out of the Dust, is make it so the Size over Life is falling over time. Just move the keyframes on the bottom to the top, and the ones on the top to the bottom basically… making it a descending curve on the graph… this will give you the desired effect. To make the effect slower or faster (as if you were moving quickly or slowly through the dust) adjust the point on the Life graph in the particle type’s properties (“Dust” again), I THINK! <-- There is probably a better way to do it than this. Alan or Elvis would know.