i'm not sure what u mean by 'outer area for an air return', but i had a question about misters... won't the mist fly out of the bong w/ airflow?
/edit: i ordered this head this morning, b/c it still has a lot of flow (more water = more cooling), and has finer water drops (more surface area).
http://gardengift.com/rainbowwand.html (just the head, not the whole wand)
im looking into data on misters...