I cannot seem to figure this out even from the ambient dust particle example. I want to fill a room with particle of dust with various sprites and behaviors. In After Effects you can add a particle generator where you can set up the size of XY and Zof the particle emitter size to fill a room. I have looked in the documentation on particle behavior values like gravity, velocity, speed but in the attribute editor of the particles, all I found where drop down menus where you would expect to see editable values.
Try checking this box (inside the particle effect’s details panel):
You should be able to scale the particle effect in the level now to fit your room’s size using the normal scale tool (R Key).
If you use the initial location module you can define a rectangle/box volume to spawn the sprites within. I highly recommend using GPU particles for this case.
Initial Location max 150, 150, 150 min -150, -150, -150 should yield you a 300 unit square volume.
Using local space will only move them around/rotate their spawn positions and transform positions with the local emitter location/rotation axis of the placed actor.
If you want the particles to be larger, you need to change the initial size.
Check out this page for a full description of what all of the modules in Cascade do.
Hope that helps you