Sorry guys there is no cut and dry answer here, but a lot of ifs.
If you have a small pet and there is only a small amount of waste, if the pet has only had an accident once in one specific area, if the spot is in a place in you room where it can get a lot of circulation.
So the answer is definitely this, carpet cleaning is not going to hurt.
Let me give you a little background to what is going on with pet odors, specifically pet urine odors.
When you pet urinates on your carpet it provides a food source to the bacteria that lives there, the urine also picks up bacteria as it passes the dermis and comes into contact with the animals fur. The bacteria breaks the urine down into food and creates in the process two byproducts; ammonia and carbon dioxide. The carbon dioxide odor molecules are small enough to become airborne by the carbon dioxide. This is the main source of the smell we associate with pet urine odors.
There is also a small amount of lipids, animal fat, which is present in the urine. This can, over time, create a greasy oily layer on the surface of the fibers of the carpet. This is significant because it means to remove the urine from the carpet you must first remove the layer of accumulated lipids. If you try to clean the spot with out removing this oily layer the cleaning agent will just sit on top of the spot or run to the outer edge.
If your pet is urinating on the same spot on a regular basis, even a couple times a month, the ammonia which is alkaline reacts to the acidic nature of the urine and creates salts. These salts are highly hydrophilic, water loving. This means that any moisture in the surrounding atmosphere will be picked up by these salts and used to help the bacteria continue to survive.
So will carpet cleaning help? If you have a small pet who had one accident, yes it will. But please be aware that it may not remove all of the problem.
If you have a large pet or a pet who has used your carpet on multiple occasions then it will still help remove the urine from the carpet, but will do little to remove the urine from the pad or the sub floor. There are more intensive treatments for that which include saturating the area with a special cleaning agent that breaks down the urine in the spot. Then removing the contaminated water with a special tool which you stand on. This tool removes the contaminated water from the carpet, the pad, and the sub floor. Next a second agent is sprayed on the area to help break down any urine that was left by the “top down” cleaning treatment.
If you have a sever case, you can still be saved. Pulling back the carpet, sealing the sub floor to prevent odor from seeping back out, removing and replacing the pad, cleaning the back and the front of the carpet and finally a heavy treatment of odor neutralizer.
I truly hope this has helped clear things up a little bit.