Incorrect smoke simulation from particle system

Hello over there,

I would like to simulate clouds with smoke simulation using Cycles but instead of “being” in 3D dimension (inside the cube), the simulation is ON the surface of the cube. Here is a screenshot and the blendfile
http://www.pasteall.org/blend/41140


Thanks in advance

the simulation is ON the surface of the cube.
You have set the particles to be emitted from the faces of the object

thanks problem solved ^^