When a technician from UpFront Home Services comes to clean your carpet you may notice that we utilize a Urine Detection light or UV light when inspecting the carpet. This light allows us to see the Urine or other biological fluids that have occurred on your carpet.
What causes urine specifically to glow under a UV light is a chemical in the urine called Phosphorus. Phosphorus is used to make LEDs and Fluorescent Light Bulbs to cause them to glow and provide light. Even when thoroughly cleaned and treated with our Urine Treatment the area may still glow under a UV light. That does not however mean that Urine or the odor associated with urine is present, it is just the phosphorus that is causing the area to fluoresce.
So in a nut shell, Phosphorus essentially bonds to the dye sites on the carpet which causes the urine to glow underneath the UV light.