I should have mentioned that OBAN does not work for strong urine smells. At least not in the short duration that I have been able to observe. That's the only situation where it does not work for me.
For urine, I am using Nature's Miracle Urine Destroyer. There are a lot of nature's miracle products. The one labeled "urine destroyer" found in the Cat section of big pet store chains is the one that works for me. It has peroxide in addition to the enzymes (don't know why the peroxide doesn't destroy the enzyme though). It doesn't work all the time either. I have found that I have not been able to clean up successfully after a thorough urine soaking down to the carpet pad.
I have heard of "restoration" companies that refuse to clean these extensive urine soakings also.