Just a quick example of options to set up indirect emission, that are faster and less noisy than relying on the brute force indirect emission sampling of the volume.
Most of the time you're just looking for temporally stable illumination that is clean, not needing uber accurate sources.
Of course if the fire/emission was to be seen in a highly reflective surface with sharp specular, you would do a separate pass with spec AOV using the original source.
