@All: Oh sorry, i was in such a rush last night i didnt explain.
The video was just to show off the new particle system and how the smoke bounced off objects, so i stuck a textured sphere in the smokes way and viola ! smoke reacts to it.

@Olsen: They do stop, just the range is quite long, they disappear when they destroy blocks and otherwise the bounce until they are out of range and dissappear in a puff of smoke, its so much easier to see in game than on that video!