That "classic" urine odor is really caused by the waste products of bacteria, so get to the problem quickly, before they have a chance to start multiplying.
Cleaning Fresh Urine Spills
On a fresh spill, blot up the moisture as soon as you can with towels, paper towels, or whatever you have that's dry, absorbent and colorfast. Don't scrub the moisture down into the carpet because it will naturally wick up to the top of the fibers and you don't want to work it down in.
Then, sprinkle Arm & Hammer® baking powder or baking soda (either one) over the damp area, covering it completely to a depth of about a quarter-inch. Don't rub it in. Use more than you think you really need, so you can't see any carpet through the powder.
Because the liquid naturally wicks upwards it will be drawn up from the fibers, out of the carpet, and into the powder. Let it sit one to two days until the powder is completely dry, then vacuum.
This should work if the spill is fresh and if it hasn't soaked into the carpet padding or the floor beneath.
Cleaning Older Urine Stains
For an older contamination that has an odor, you really only have two choices: professional cleaning or kill the bacteria growing in the carpet. If your carpet is made of wool or nylon, then you will probably need professional cleaners because products containing bleach will take the color out of nylon, and bleach will dissolve wool.
If you have carpet made of Olefin® or polyester, you can mix a solution of 1 part bleach to 10 parts water and soak the affected area with a trigger sprayer. After this mixture has had a chance to work for a couple of hours, then apply the blot, Arm & Hammer®, let it dry, and vacuum as above.
Nylon and Wool Carpets
Reminder: don't use bleach if your carpet is made of nylon or wool. If you aren't sure, don't do it. If you think you're sure, test this on an out-of-the way spot first, just to be certain.
If you have nylon or wool carpet and the spill is old and smelly, you can try thoroughly re-wetting the spill with water and then using the blot, Arm & Hammer®, vacuum method, but your chances of success are greatly reduced because this won't kill the bacteria actively growing in the carpet. You'll probably have to call in a professional.
The best cure is prevention, of course.
Pet urine can cause permanent damage to your floors and fabrics. It can also create an unhealthy indoor environment. When urine is first deposited onto a floor or fabric, it has a pH of about 5 or 6, which is on the acid side of the pH Scale. It is easier to remove right then when it is fresh. Once it dries it turns “alkaline” or to a high pH between 10 to12 on the scale and becomes more difficult to remove. The warm acid state of the urine offers a perfect breeding ground for bacteria, which begin to flourish almost immediately. In this original acid state the urine begins to oxidize and react with the carpet to create a color change, which will become permanent if the urine is not removed immediately. Some of this color change can be attributed to the strong ammonia that forms as the urine passes through bacterial and chemical change. If left for days or weeks, depending on the fabric or floor type, it will change the dye structure, therefore causing permanent staining. Even if the soluble deposits are removed, the damage to the dye structure may already be done.
There are two sources of odors associated with urine. The first comes from bacteria that grow abundantly in dark warm places with a never-ending food source. A pet can feed the bacteria daily! This bacteria growth and breakdown of the urine creates amino acids. These complex organic compounds will often work deep into the fibers to a point of becoming part of the fiber. This can present a challenging situation. The waste materials and gases from the decomposing urine create an unpleasant odor. When dried urine is remoistened, it gives off an ammonia gas. If smelled once it is seldom forgotten.
The second source of odor is chemical odor that is present even when the bacteria have been killed. This explains the reason that more than sanitizing is necessary toneutralize odors from urine. Urine also presents additional odor problems when the relative humidity is high.The salts and crystals that are left behind as the urine dries are hydrophilic and draw water to them. Dried urine is often easy to smell in the humid months because the salts attract the moisture, the moisture evaporates putting out a greater proportion of odorous ammonia gas. You must get rid of the urine salts in and under the carpet to get rid of the odor. That’s why cleaning existing urine spots WILL NOT remove any associated odor. In fact, it could INCREASE the odor in the air space for a temporary period of time.