Particle systems, just like other entities, can have parent-child relationships. The entity info_particle_system can be parented to any entity, but particle systems within a .pcf file can also be parented to each other. To demonstrate this, let's create a quick smoke effect to add to the fire.
Instead of creating a whole other smoke effect from scratch, we can just copy and modify the fire particle. In Particle Editor, select the particle system myfire01, and click on the Copy button. Type mysmoke01 for the new particle name and click on OK.
Now we have an exact copy of our fire particle system with a new name. Select the new particle system and let's turn it into a smoke system.
The first thing we want to change is the material. In the main properties, browse for the material particle | smoke1 | smoke1_additive.vmt. You'll see the fire change to smoke. But we're not done quite yet. When there is a fire, smoke doesn't appear immediately;...