Quote Originally Posted by jdmls88 View Post
whats the filter in the back?
It's an activated charcoal filter. Fresh air is vented in through 2 - 2" holes on the bottom left, then it's blown out through the filter to kill any odor. It exhausts through a 4" hole with a small vent cover on the outside. Here's the link to the plans for a free standing air purifier using one of these.

http://ball-pythons.net/forums/showthread.php?t=55074