How to make something like the Gas in H1Z1?

I am currently searching for the best way to create something like the gas in H1Z1. The programming isn’t the problem but the way to visualize it. Using Particles creates the problem of the particles turning towards the player and therefore not making up a clear line/border. Any Ideas on how to create this effect? I also thought about post processing but I have no Idea about that.

Thank you in advance,