Have you tried sealing the concrete with a a kilz product or other sealer. It will take that to neutralize the odor in the slab. While you're at it, I'd also seal all exposed wood. After you seal it, the smell should be gone. Are you sure it's not permiating from another room? Did they wee on the return AC/Heating vents, if they are available?

I can confirm that Kilz will seal the area, cutting off all odors. However, if you must "find" the odor, a Black Light will do. The kind that kids use to look at posters. Make sure the Black Light is a flourescent tube type, not the regular light bulb shape. If you turn on a Black Light of this type (probably available at a Party Rental place, and some pet stores just for this purpose) the urine will show up, just like a CSI crime scene. Get ALL of it covered in Kilz. Check higher up the wall, window sills (maybe they had a cat).

Kilz WILL work. MAKE SURE you get the correct Kilz for this: KILZ Original, interior oil-base formula.

By the way, in our experience Nature's Miracle did NOT work.

Good luck.

Here is a link that might be useful: This is the Kilz Product

The AC/heating is all in the attic/ceiling, so (fortunately) that is one source that can be ruled out...

I have shut all the doors to the room and left for a period of time. When I open the door, I smell the odor, so it is in that room. I do not smell it in the air in other rooms of the house.

I have not sealed the floors because there is as much literature against as there is for. And the sealants are not guaranteed for an extended period of time (typically 3 - 5 years max).

I'm in the Houston area, so it is already summer here. I've intentionaly left the house warm so that the humidity will be high allowing odors to flourish. The smell is not nearly as bad as it was when the carpets were first removed. So, I know I am making headway. It is just so frustrating to smell an odor and not be able to locate the source. Is it possible the odor itself permeated the walls/ceiling even though those areas were not urinated on?

My next step is to use a garden sprayer to apply the odor neutralizer (Expel)to all the walls and the ceiling in that room. Those are the only surfaces which have not been treated, yet. (For the slab, I have been scrubbing with MM2 (a bacterial/enzymatic cleaner), vaccuming up the suds/liquid and then reapplying MM2 and allowing it to air dry.)

Lucy, you might check the doors. Dogs will often hoist their leg, as you know because you replaced the bottom foot of sheetrock. Also, if that room has smelled like that long enough, it may be that the odor has permeated the paint on the walls and/or ceiling.

We bought a little house to use as a rental and it was like that. There were hardwood floors under the carpet and the carpet was so bad there was mold under it and the pad. To say the least, some of the hardwood was in pretty bad shape. I used peroxide and it helped a lot with the smell. Had to replace some of the floor. Sealed and repainted walls and ceilings. No dog smell now.

I agree, Natures Miracle stinks!