I used to do "Disaster Remediation", and while it was mostly Fire/Water damage, I would get the occasional Cat call. A guy who owned a 2-flat kicked out a crazy Lady with 25 Cats that shat/pissed everywhere (except their litter box). That was the only time I was ever unable to mitigate a pervasive odor. They eventually had to gut the place. The molecular structure of Cat piss makes it the perfect vehicle to fuck up anyone's home.