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How to Locate and Clean Pet Urine In Carpet


In this post, I'll show you EXACTLY how to use a UV flashlight to find and clean up pet urine accidents in carpet.

Urine is made up of many different types of molecules like urea, uric acid, creatinine, citrate, sodium, potassium, ammonium, calcium, magnesium, oxalate, sulphate, phosphate, phosphorous, urobilin, possible bacteria, and other molecules. 

Each one of these molecules has unique properties. For example, the yellow color comes from a molecule called urobilin, other substances like bacteria and urea are responsible for the odor.

When urine accidents are observed under an ultraviolet (UV) light (also known as a black light), the urine stain will glow. This glow is known as fluorescence.

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I'm Jimmy - a professional carpet cleaner sharing my stain removal tips and tricks with everyday people.

What Does a Urine Stain Look Like Under a UV Light?


A UV light can be used to easily locate urine accidents in carpet thanks to a molecule in urine called phosphorus.


Phosphorus molecules absorb UV light from the UV flashlight, and then emit visible light back into your eyes. This causes urine stains to glow under a UV light. 

When using a UV flashlight to locate pet urine accidents, it is best to do so when the room is dark. The darker the room, the brighter the urine stains will glow. 

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What Other Types of Stains Glow Under a UV Light / Black Light?


UV lights and black lights don't just cause urine stains to glow. In fact, anything that was spilt in your carpet that contained the molecule phosphorus will glow under a UV light. 

Stains that glow under a black light: urine, blood, seamen, soaps, detergents, Mr. Clean, Lysol, other cleaning solutions/products, turmeric, coffee, beer, many alcoholic beverages, and milk products. 

This means that the stains that show up under a UV Light might not necessarily be caused by urine.

How to tell which glowing stains are caused by urine? Well the best way to do it is to use your nose. 

First locate a glowing stain with the UV light, then bring your nose close to the stain and give it a smell. 

If the area smells like urine, the proceed to the next section for step by step instructions on how to thoroughly clean a urine accident. 

How to Clean Up Pet Urine Stains In Carpet?


If the urine stain is fresh, grab a stack of white cloths, or paper towels and use them to absorb as much urine from the carpet as possible.


Place a dry white cloth on top of the urine accident, then apply pressure to the cloth to absorb as much urine from the carpet as possible. Keep repeating this step with dry cloths until urine stops coming out of the carpet. 

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When it comes to choosing a cleaning solution, the best option is to use an enzyme cleaner.


Enzymes exist in plants, animals, our digestive systems, and their purpose is to break down organic matter by acting as a catalyst. This makes enzyme cleaners perfect for cleaning biological messes like urine, blood, vomit, and feces. 


Enzymes also work great at eliminating odors by breaking down molecules that cause odors. Most enzyme cleaning products contain an enzyme called urease. Urease attacks and breaks down urea molecules, which eliminates urine odors.


My preferred enzyme cleaning product is called Biokleen Back-Out Stain + Odor Remover.

The directions to use to use Biokleen Back-Out are simple:

1) Saturate affected area with Biokleen Back-Out.

2) Let sit for five minutes or more. 

3) Blot affected area with a rag. 

4) Repeat the process if necessary. Does not need to be rinsed. 

Are Stains That Appear Under a Black Light Permanent?


The short answer is no, these glowing stains are not permanent. The phosphorus molecules that cause the stains to glow under a black light can be broken down using an advanced oxidation reaction.


When things like urine, beer, or other substances that contain phosphorus end up in our carpets, the phosphorus molecules typically become permanently bonded to the carpet fibers.  


Below, I am going to show you a method that can be used to remove these glowing stains, but first let me say there is generally no real reason that they need to be removed.


Let me explain...

When a urine stain on carpet is thoroughly cleaned, most of the urine molecules (urea, uric acid, creatinine, citrate, sodium, potassium, ammonium, calcium, magnesium, etc.) will come out of the carpet. 

The phosphorus molecule, on the other hand, happens to be extremely sticky and will typically easily bond to the carpet fibers. This means that most of the phosphorus molecules cannot be cleaned out of the carpet.


Even if you hired a professional carpet cleaner and paid for their most expensive urine treatment package, the urine stains would still glow under a black light after the cleaning. 

Phosphorus is harmless, odorless, colorless, and the only way you would know it is in the carpet is if you are using a black light / UV light to detect it. My recommendation would be to just clean the urine accidents using an enzyme cleaner, and don't worry about removing the phosphorus.  

You may still have a desire to make these glowing stains disappear, so I'll show you a way to remove stains that glow under a black light below. 

How to Remove Stains That Appear and Glow Under a Black Light?


The phosphorus molecules that cause these stains to glow under a black light can be broken down using an advanced oxidation reaction.

To create an advanced oxidation reaction, you'll need 3% hydrogen peroxide and a UV light. 

UV Light causes hydrogen peroxide (H2O2) molecules to split into hydroxyl radicals (OH-), then the hydroxyl radicals break down the phosphorus molecules. 

Once all of the phosphorus molecules have been broken down, stain will no longer glow under a UV light. 

The step-by-step instructions for this are identical to how to remove turmeric stains from carpet

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