I went to the Dentist and he put an experimental sealant/whitener on my front teeth. He had a little device, and I noticed the Violet light coming out of the end. He used that to set the sealant. I asked him about the source, and it's from LED(s). Looked on the Internet, and sure enough they have UV LED's. Wonder how long before someone makes a UV sterilizer for HVAC applications?