There are a variety of reasons that pet stains are so hard to remove. For starters, when animals urinate on the carpet they are putting down an acid. The acid will eat right through any carpet protector you might have and penetrate deep into the fiber where they will be difficult to remove.
Another reason that they are so difficult to remove is because of the volume that they put down. They put down so much liquid that the surface fibers can not absorb it. This means that it penetrates the carpet fibers and will go into the backing, the pad and the sub floor. This really complicates the cleaning because it is easy enough to clean the surface but much more difficult to clean under it.
Professional carpet cleaners Denver do have methods of sub surface cleaning but they are pricey and still might not remove all of the material. The only way to really solve the problem completely is to pull the carpet up and replace the pad and clean both sides. This is a time consuming and expensive process.
The last reason that urine can be such a problem is that it contains bacteria. This is what produces the odor. It is feeding on the urine and releasing ammonia and will continue to do so until you remove every bit of the urine. Check out the 4 STEP PET Stain Removal process here.
