GermGuardian® LB4000 UV-C Replacement Bulb is a 5-watt bulb. UV-C light helps reduce airborne bacteria, viruses, mold spores*, and works to reduce volatile organic compounds. *Tested with Staphylococcus Albus, and Escherichia Coli, Aspergillus Niger, and Phi-X174. This bulb needs to be replaced every 10-12 month depending on use and environmental factors. It can be used for the GermGuardian® Air Purifier Models AC4300BPTCA, AC4900, AC4825, AC4850, AC4870, AC5300B, AC5350B, AC5350W, AC5900, CDAP4500, and CDAP5500. The use of this genuine Guardian Technologies™ replacement part will maintain the product's performance.