I believe Bruce (the Mod) posted something about a Febreeze plugin that he's tried and is very impressed with. It cleans the air but doesn't leave behind some gawd awful flower-over-rat-poop scent behind. I think that combined with a room with good ventilation and the ability to open a window plus a good cleaning routine works just fine. I know in my home I have well over 100 or so rats at any given time, yet my worst struggle is with cat litter boxes for our two darned cats.