Honestly? I think they go nose-blind to it after a while. This past summer my husband and I were looking for home daycare for our son, and one home we went to reeked of cat urine. Just reeked. And I used to work at a vet clinic, so I'm probably not as sensitive to the smell as most people... so if I say it's bad, that means it's bad. And the homeowner/daycare provider didn't even seem to notice. And yes, it was an obeast.