I have an old house with very old wall to wall carpets. The carpt by the front door is just awful, and I have been trying to clean it for a while, with poor results. Recently, however, my kitten, who is not yet house broken, peed on a spot on the carpet, and it was immediately cleaned of all the old dirt (the pee needed cleaning up, of course)! Since I have no plan to make the kitten pee everywhere, does anyone know exactly what in the pee cleaned the carpet, and maybe how to duplicate the effect in a more sanitary way?
Urine (human and animal) contains ammonia, paricularly if it's left for a while, e.g. if you didn't notice it at first. Ammonia is used in carpet-cleaning products. In fact it's been used for stain-removal since Roman times.
You might want to track down an ammonia-based carpet cleaner, but use it when you can open all the windows and sit outside for a bit afterwards.