A method and system for monitoring conditions of a rack of animal cages. An animal caging system including a plurality of animal cages removably connected to an exhaust. Collection media is removably mounted in an exhaust plenum of the rack using a holder. Exhaust air dust clings to the collection media as exhaust from the animal cages flows along the length of the collection media. A door to the exhaust plenum can be opened and the collection media can be removed from the holder.
