I use dunnage (un-printed newspaper) in racks and pvc caging for a few different species. Because of these being encased enclosures I never had any issues with humidity however I am currently in an area that has natural 50-60% humidity. When I had my amazon tree boas on it, I would sometimes mist when I'd notice a shed cycle starting but never did anything special to raise humidity. If you are using it in a glass tank with an open mesh top, you'll want to cover as much of the mesh top as possible with plexi (or something) and possibly provide an extra water bowl in the warm end (over/under the heat source) as well as misting either weekly or daily depending on your needs. I've used it in tanks before and that is what I did.