The area I had a problem with has dark carpet so stains didn't show and I'm sure clean up was often missed so some accidents set in. I tried many products over time. I used carpet machine often. I rinsed with water. Rinsed with vinegar. I worked at this regularly but even when it seemed I had success the pee smell returned. So first day with MPP I saturated the area, opened window, turned on a fan and closed the door. Smell got worse before it got better but I could still smell pee. I repeated the process again it was worse before better but over all better. Third time I used carpet cleaner with hot water only then saturated damp carpet with MPP. Oder came out but by end of day. Following day I left the house all day and room was closed I opened door and no odor at all!