Locating the Source of a Smell in Our House?

We rescued a dog who we soon discovered peed everywhere, even after being taken out. What we didn't realize (we had recently bought our home) is that the floors slope slightly into the wall. The walls are concrete and plaster, but there is a half inch gap between where the floor ends and the baseboard begins. We have sprayed animal enzyme multiple times, used a charcoal fan, and it just came back. Now we are smelling the same smell on the other side of the house too. Any advice?