Every spring and summer, when the air shaft window was open, our apartment was invaded by the stench of urine. One weekend morning we noticed the cat litter overflowing from its bag on a broad ledge two floors down, across the airshaft. How he decided to start throwing condoms full of bleach-water at it, I don't recall, but it became a frenzied activity. He stood buck-naked in front of our curtainless kitchen window hurling these bombs through the opening, trying to hit the target. This went on until the supply was gone. Several weeks later we learned that the upstairs neighbor kept a dog indoors - all the time. The malodorous source was directly above us and had nothing to do with the cat litter across the way. air shaft, dog, urine, smell