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Urine Stains and Odors: Old vs New
One of the most important issues with urine stains and odors is to understand the difference between fresh urine deposits and stains that have been there for a long time. 

Fresh urine includes a yellowish pigment called urochrome. When it is deposited on fibers, it stains the fibers yellow. No surprise here. 

In just a few days after urine is deposited, microbial activity begins to decompose the urine. This process releases ammonia gas. It’s chiefly the ammonia that creates that distinct pungent odor we smell when we encounter urine contamination. 

Ammonia has a pH of around 12.5. A pH this high has the ability to break down or degrade the dye base of nylon carpet fibers. Although today’s new polyester fibers are not prone to color loss, concentrated ammonia can actually bleach out the color dyes used in nylon carpet fibers. In sufficient quantities, ammonia can break down all the dyes in a carpet, leaving only a yellowish white color in the fibers. 

In a recent technical bulletin called "Pet Urine and Carpet," The Carpet and Rug Institute describes the color change process this way: 
Urine can affect the dyes used in carpet, although not all occurrences will result in a permanent stain. Success is dependent upon the content of the urine, the dyes, and any treatments applied to the carpet during manufacturing, the finish used, and the time elapsed after the deposit. Some urine spots may be immediately noticeable, while others may take weeks or months for a reaction. The dyes may change color immediately after contact with urine. When urine spots develop slowly and are noticed after much time has elapsed, the dyes and carpet fibers may be permanently damaged. In beige carpet, blue dyes are attacked by pet urine, leaving behind the red and yellow dyes with a resulting stain appearing red, yellow, or orange. (Download the CRI bulletin here.)

It’s easy to confuse this loss of color with the yellow urochrome pigment stain originally deposited with the urine.

This is why the most important question we can ask the customer is “How long has this stain been there?” A urine stain that has been present for more than a year may be no longer be a stain; it may be a loss of color, and this requires repair, not just cleaning.  

If you can communicate this critical difference between new and old urine deposits to your customer, you’ll help to build trust in your cleaning expertise and ability. Plus, you’ll create realistic expectations about what can be cleaned and what might need repair or replacement.