Periodically, we have a dead animal smell in an outside wall at the end of one bedroom next to a bath. It would be a very strong dead animal smell that came around every few months. At first I thought it was a dead mouse but it was always in exactly the same place on the outside wall.

For years the bath next to this area was unused. The smell did not come up through the shower drain but it did seem to stay away when the shower was used daily. However, when the smell was there, just putting water down the drain or covering the drain did not help. In fact the smell has always seemed to be in the wall not the drain itself. The shower and drain are about 5 feet from the wall.

I thought perhaps it was back flow of air from a roof vent pipe that is at that area of the roof but once again, how would it get in this outside wall? I am stumped. I'd be happy to call a pro but I don't know what I am hiring them to do.

Can anyone help me?