Black lights, or ultraviolet lights, are inexpensive and often available at large department stores. Black lights are useful for home cleaning because they kill microbes and detect stains invisible under everyday incandescent or fluorescent lights.

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Ultraviolet light can kill microbes and detect invisible contaminants.

Cleaning Urine Stains

Urine is notorious for soaking into carpets and smelling up rooms--or entire houses--even after it has been cleaned. This is because urine stains are hard to see with the naked eye and therefore difficult to clean completely. These stains cannot hide from black light, however. Darkening a room and shining a black light will quickly highlight where urine remains, letting you know when the stain is really gone.

Cleaning Walls

The Institute of Nanotechnology reports that applying ultraviolet light to white walls can kill deadly germs on contact. White paint often contains titanium dioxide particles, whose electrons are excited by ultraviolet light. This excitement triggers a reaction with water molecules present on almost any surface, killing microbes.

Black Light for Cleaning Machinery

Black light is an important resource for detecting contaminants on machine parts that must meet strict cleaning standards, according to the Pacific Northwest's Pollution Prevention Resource Center. Small machine parts are passed under ultraviolet lights, which immediately notify inspectors of any contaminants that fluoresce, or glow, under black light.