Philips 210641 18-watt PL-L TUV Germicidal with  4-Pin Base Light Bulb For residential drinking water, water and air treatment units, stand-alone purifiers and deactivation of bacteria, viruses and other micro-organisms Short-wave UV radiation with a peak at 253.7 nm (UVC) for disinfection purposes Lamp glass filters out the 185 nm ozone-forming radiation Warning sign on lamp indicates that the lamp radiates UVC 2G11, 4-pin Base