Basically what this is, the particle was added onto the env_explosion entity.
That means any rockets, explosive barrels, and bombs will use this particle effect added onto the regular one.
It will be more laggy of course if you blow up 20+ barrels but this is a great effect for pretty much anything from npc wars to machinimas.
For some reason whenever I blow up a lot of zombies with this the game will crash, maybe its just other conflicting addons but if it does crash for any of you (blowing up zombies) please tell me so I can reduce the amount of particles.
edit: lol im stupid i forgot i didnt even give the dl link yet...