Cleaned the area but still smell urine odor?

Cleaned the accident area with soap and water many times why do you still smell the urine odor from time to time? In a dry state urine salts have no odor. Anytime the urine salts are exposed to humidity or dampness they re-activate with a strong odor. So the next time your at your local pet store, purchase an odor remover product. I too use to just walk past these products, until I fully understood how the salt crystals will re-activate.