I know you didn't ask me but I'll tell you that I have 8 litter boxes, one for each cat plus one. Plus I have one in the guest room for Puddy because that's where she sleeps because I have to keep a close eye on her due to CRF. No air purifiers; I figure the pee cats will do their thing on the air purifier, too, so why bother? Having multiple litter boxes definitely helps.