This shader is considered deprecated and will be removed in a future release. You should use the Standard Volume shader instead.
The Volume Collector only works with an object's bounding box (and internally bounding sphere).
It is recommended that volume shading networks are kept as lean as possible. This is important for render times in the volume context because it is evaluated so often.
The sampling tab has additional parameters to control how data is sampled from volume channels.
Ensure that the emission attribute is driven by a VDB grid. If it is a fixed parameter value you may get artifacts.
Volumes can only receive indirect lighting from other emissive volumes when the Volume Ray Depth is above 0.
Further examples using the volume collector shader ('God rays' achieved using Volume Scattering).