I looked at the instructions for "Nature's Miracle Stain and Odor" and the second paragraph says -
How it works:
Nature’s Miracle Stain and Odor Remover goes to work quickly to break down tough stains and odors. Our bio-enzymatic formula specifically reacts to organic stain and odor matter and works to eliminate any traces—unlike other products that may simply mask stains and odors. Because of this reaction, it is important that Nature’s Miracle Stain and Odor Remover is allowed to dry naturally (sometimes taking up to two weeks) and that it reaches all of the stain, including carpet pads and subfloors where the stain and odor can spread far beyond what is visible.
I also found this -
For stains that have already set:
Consider renting an extractor or wet vac to remove all traces of heavy stains in carpeting (get one from a local hardware store). This machine works much like a vacuum cleaner and is efficient and economical. Extracting/wet vac machines do the best job of forcing clean water through your carpet and then forcing the dirty water back out. When you use these machines or cleaners, carefully follow the instructions. Don't use any chemicals with these machines; they work much better with plain water.
Use a high-quality pet odor neutralizer once the area is really clean (available at pet supply stores). Be sure to read and follow the cleaner's directions for use, including testing the cleaner on a small, hidden portion of fabric first to be sure it doesn't stain.
Try any good carpet stain remover if the area still looks stained after it's completely dry from extracting and neutralizing.
Avoid using steam cleaners to clean urine odors from carpet or upholstery. The heat will permanently set the stain and the odor by bonding the protein into any man-made fibers.
Avoid using cleaning chemicals, especially those with strong odors such as ammonia or vinegar. From your pet's perspective, these don't effectively eliminate or cover the urine odor and may actually encourage your pet to reinforce the urine scent mark in that area.
Neutralizing cleaners won't work until you've rinsed every trace of the old cleaner from the carpet if you've previously used cleaners or chemicals of any kind on the area. Even if you haven't used chemicals recently, any trace of a non-protein-based substance will weaken the effect of the enzymatic cleaner. The cleaner will use up its "energy" on the old cleaners, instead of on the protein stains you want removed.
Your job will be more difficult if urine has soaked down into the padding underneath your carpet. In some cases, you may need to take the drastic step of removing and replacing that portion of the carpet and padding.
