Do you know that you can get a black light to check out body fluids? It is actually a very good way to check out for pet urine or make sure that the bathroom you are using or hotel room you are occupying is really clean.
In particular, cat urine glows particularly brightly under ultraviolet light. Urine glows under the black light mainly because it has the element phosphorus. Phosphorus glows quite yellowish green in the presence of oxygen, with or without black light, but the light gives additional energy that make the chemiluminescence easier to see for anyone. Urine also has broken down blood proteins that glow under a black light.