,one start:http://www.biggerpockets.com/renewsblog/2012/11/5/...also start with : cat odors or cat smell or cat urine in the forum search.but after you get rid of smell, you need to seal the concrete before anything else.also, 2 dozens of donuts, some sample pets treats and couple hours of chit-chat at the local pet-shelter will get you more info about what is used in commercial pet settings. also regulations....also don't forget to get friendly with the building neighbors...

-Noticeable but not terribly strong pet odor throughout house, which according the guide, is considered damage...Things I'm not sure about:-Walls and doors are dirty in many parts of the house.

Turns out they had masked the odor pretty well with incense, perfume etc.

Many times, I asked for a dozen offers to go out and the agent never grumbled .....

I would use a professional grade ozone machine to remove any odors.

What if you smell a foul odor or smoking?

Check for strange odors either outside near the tank or inside the house.2. 

I am also concerned the extreme odor can seep into materials like the ceiling tiles, but would try the wall treatment first.

That would fall under "noxious odors".Paying her to relocate might be best and a signing that lease is terminated with the agreement and as soon as you have the keys when the relocation happens you change the locks for all entry doors immediately.

High levels, and low levels, of chlorine will both produce strong odors.