This scientific article examines the photochemical degradation potential of mercury-vapor discharge ( Ultra-Violet fluorescent ) lamps. Three types of radiation can be identified: Fluorescent light produced by the powder coating on the glass tube, light emitted from mercury-vapor discharge and invisible Ultra-Violet radiation. Emissions from the mercury-vapor discharge are discontinuous while that given off by the powder coating is continuous. Radiation in the range 254 millimicrons ( nanometers ) causes intense photochemical reactions. Only Ultra-Violet lamps can emit close to this in the 260 to 310 nanometer region. Studies carried out on 78 lamps of 28 different makes show that all of the lamps emit the region extending to 280 - 290 nanometers. In the region of 300 nanometers spectrum contains lines and sometimes a continuum that is considered more damaging. Soft white and warm white have continuous wavelengths well into the Ultra-Violet region and are more dangerous than those that emit in only a few wavelengths. It is generally found that after approximately 1000 hours of illumination there is a reduction of 25 percent in the intensity of extreme wavelength lines. This examines Ultra-Violet tubular lamps for use in Museums.