Problem with solid objects for smoke

I have the domain and smoke object problem worked out. I can render smoke, but the objects that emit the smoke inside the domain stay solid.

What can I do to make those objects disappear.

I set up several spheres inside the domain and joined them as 1 object to make the smoke. There is no material attached to the spheres.

I managed to solve this by turning the smoke object rendering visibility off in the outliner. Can someone confirm for me that this is the proper way to do so? I’m using Blender Internal.