Osram Puritec HNS G5 6W G6T5 lamps emit high intensity uv-c light at 254nm. They purify air, water, and surfaces without the use of harsh chemicals that are harmful to the environment. This ultraviolet light is very effective and will eliminate 99.9% of micro organisms. After 9000 hours or 12 months, the amount of useful light emitted will decline. Hence, we recommend replacing your lamp every year.