If you have human urine in your carpet, you have a tricky problem to solve. Urine contains salts that attract and hold moisture better than most materials. Even if the urine has been left to dry for weeks or even months, you will find the area where the urine is has a higher moisture content than other unaffected areas, not to mention that it will smell.
Lift the carpet where the urine smell is. The bottom side of the carpet will have watermarks from the urine on it. Use a mixture of one part vinegar to five parts water to clean the underside of the carpet. You can also buy products that have already been mixed.
Using a carpet knife, cut out the part of the pad that is affected by the urine. Cut it out in a square so that the pad will be easy to measure and replace. Wash the floor in the area where the pad was removed, using the urine treatment mixture. Allow the floor to dry for about an hour.
Put in some new carpet pad in the area that was removed. Cut the new pad to the dimensions of the square hole that you made in the carpet pad. Lay the carpet back down on the new pad. Once the carpet is down, shampoo the entire carpet with the urine treatment product. You can rent carpet shampooers from supermarkets and home improvement stores.
Allow the carpet to dry thoroughly after shampooing the carpet. This will take from one to four days. You can use fans in the room to speed the process.