duct work?

in lieu of a PVC pipe covering in fleece, what are some feelings about using (uncovered) ductwork as tubes in cages? i thought i saw it in someone's pictures in the Ferret Nation Club thread. it'd be a good option for cooling chins, like the chinchiller or granite slabs. just curious if theres a big reason not to use these.

link to picture of what I mean:
http://ift.tt/2fI4kUc