I highly recommend this product!!! I had two cats that I rescued from local humane societies. They grew old with me and both ended up with diseases, one was diabetes and the other was hyperthyroidism. As all pet owners know, when cats become ill, sometimes they start urinating outside their litter boxes. The one with diabetes was a male and he did this every time he had to relieve himself, spraying all over the wall which ran down the wall and into the carpeting. The other was a female and only started going outside her box in the last month or so of her illness before she passed away. Both cats have since passed on and it has been a real struggle getting rid of the odors left behind. I have tried just about every product out there to help with this. Recently, when I commented on a post here on FB about my struggle, someone suggested to me to try this product, saying they had had the same problem and this was the only thing that worked, so skeptically, I ordered some.... a whole gallon, as the problem was that bad and I had no idea how much I would need. The offending areas were along two perimeter walls, with one wall containing a heater element from boiler heating. I used the product as specified and noticed a sharp increase in odor. The directions state that this is normal, so I let it dry and repeated the application. Well, so far I have used nearly 2 gallons (yes, it was that bad) and as of this morning, the smell is almost completely gone! I am AMAZED! Nothing else has even come close to doing this much! I am going to purchase one more gallon, just to be sure. The last application is not completely dry yet and there is barely any odor at all, but some, so I want to have more on hand just in case! I absolutely LOVE this product and would recommend it to anyone!!