UV light bulbs are fluorescent tubes with a dark blue or purple filter to remove other parts of the spectrum and leave just UVA light. UV (ultraviolet) light bulbs are often referred to as black light bulbs, or BLB (blacklight blue) bulbs. UV lights feature small wavelengths that are measured in nanometers (nm). Nanometers often affect the UV light bulb, with the bulb emitting either UVA, UVB or UVC UV radiation. None of these bulbs can penetrate human skin and safe to use.