A black light can detect invisible organic stains. Black lights are often used to detect invisible pet stains such as urine and feces, and they are sometimes used in hotels to detect bodily fluid stains left behind in the rooms.
Black lights are useful in a number of situations. They can be used to detect counterfeit money and air conditioner leaks as well as detecting scorpions in someone's home. Black lights can even detect if a piece of art or antique glass is authentic.
Carpet cleaning services sometimes offer black light service in a home or business. When using a black light, these services know where to concentrate their cleaning efforts, but today, black lights can be purchased and used by anyone.