In this house we have central air. I checked the filters and used this little brush thing to clean out the water collection hose, but I'm wondering if maybe the smell could be stuck in the duct work. I suspect that their dog peed on the air intake - it was rusted at about the right height. I bought a new one but maybe I should also take a scrub brush to the duct work.

I so hate filth. These people were supremely nasty; you can go to my profile and click on the picture - it will take you to the thread that has pictures of the grossyness that we've been cleaning.