Volume shaders allow you to visualize a 3D scalar data field (e.g. density field) by sampling field values and mapping to color and opacity. You can assign volume shaders to volume shapes (e.g. Arnold Volume object or Turbulence FD container).
Atmosphere shaders are special volume shaders to simulate a light scattering effect in the scene, like fog. Atmosphere shaders have to be set in Arnold Render settings > Main > Environment > Atmosphere field.
For more information on volume workflows refer to the Volumes page.
Below is a list of volume shaders available in C4DtoA:
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.