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Ultraviolet Frequently Asked Questions

What Is Ultraviolet Light?

Ultraviolet light is invisible to the human eye. It is part of the electromagnetic spectrum that lies beyond the purple range of the visible spectrum. The ultraviolet (or UV) spectrum has wavelengths between 100 and 400 nanometers (nm). The UV spectrum is further divided into wavelength ranges named UVA, UVB, UVC:

UV Spectrum

UVA: sun tanning, testing, inspection, insect traps, stage effects, blacklight, phototherapy (315-400nm)
UVB: sun burning, inspection, analysis, testing, phototherapy (280-360nm)
UVC: germicidal (253.7nm), ozone producing (185nm)

Phototherapy for treatment of skin diseases uses bulbs emitting in the UVA and UVB spectral range. There is also non-UV phototherapy for treatment of infant jaundice. These bulbs, "bili lights", are low or non-UV emitting fluorescent or halogen sources with strong blue light in the visible spectral range of 425-475nm.

Warning: UV radiation is harmful to skin and eyes.

Can UV Lighting be Used for Water Purification?

Water purification may seem an unexpected topic for a lighting newsletter. However, increasingly, as studies show that chemicals like chlorine are losing the fight against certain pathogens, talk turns to using ultraviolet light. The EPA recently called on municipal water suppliers to treat water with UV radiation to inactivate key pathogens such as adenovirus and other viruses, as well as bacteria and parasites such as Giardia.

What's good for city water is also good for a whole host of other applications such as hot tubs, swimming pools, water gardens and aquariums. Ultraviolet germicidal lamps produce energy at 253.7 nanometers. Lamps used for water purification also emit radiation at 185 nanometers for ozone production. These wavelengths are not visible to the human eye, although germicidal lamps also emit some visible light.

The lamps are rated by UV output in watts (not to be confused the wattage of the lamp). If you have either water or air purification applications, see Topbulb's extensive line of ultraviolet lamps. Call us if you need help with UV lamp issues.