Moist paws make big smells
Even if your cat is very good at using a litter box urine, feces, and dust for the litter itself will escape the litter box by air or the paws of the cat itself walking out of the litterbox. So it often also true there are time that the cat will not use the litter box if it is very dirty or does not have access to the box. The final result is that cat odor is not contained to the litter box itself.
The best way to explain dander is that it is microscopic pieces of dry cat skin which becomes airborn when the cat cleans itself as a rule. Cat Dander is a major offender to people with allergies and can cause a very uncomfortable environment for that person. Simply vacuuming most often than not just moves the dander around in the room of currents of air to be deposited somewhere else.
To effectively remove cat dander you should contact DFW Steam Cleaners to steam your carpet which will suspend the dander from floating on the air currents and then extracted with our high capcity vacuum system to git rid of the dander. In addition the steam will kill and neutrilize any smells that the cat tracked out of the litter box or never had time to get to the littler box in the first place.