Ultraviolet rays are harmful to organic tissue. You can see this whenever your skin burns from the sunlight. UV germicidal lights harness this power and use it to kill organic pollutants that circulate through an HVAC system. The radiation from the lights interferes with the cellular structure of organic tissue, and this kills or renders inert such contaminants as viruses, germs, bacteria, mold spores, and microbes without using any harmful chemicals.

Don't worry: the power of these UV lights isn't harmful for people or pets, just the tiny "pests" you most want to get rid of. The lights are hidden out of sight in your ducts so you won't even notice them.