This 40 watt ultraviolet air purifier lamp uses UV-C light to inactivate and kill bacteria, molds, protozoa, viruses and yeasts. This replacement germicidal bulb is a 4 pin type. Used in commercial, industrial, residential and recreational HVAC disinfection systems. This ultraviolet purification lamp is instant starting and utilizes a coil filament which operates hot. The UV lamp life is governed by the life of the electrodes and is affected by the frequency of starting. The fixture is high quality with a long lifespan.