Peder Norrby explains how to create volumetric type smoke in After Effects using his Trapcode Particular plugin.

AE/Particular Volumetric Smoke Tutorial from Peder Norrby on Vimeo.

“This was an attempt at creating a volumetric looking smoke effect, similar to this It was totally improvised so it shows how I experiment to get the settings right. After rendering the final clip I noticed I had to change the Particle>Size over Life curve so the particles size faded out rather than just disappearing abruptly. I also setup Aux>Opacity over Life so the auxiliary particles faded out (using opacity). Final render: More info and AEP here:”