UV light is a natural product of the sun. When people get sunburned, they suffer from radiation burns from a type of UV light that is emitted from the sun. The redness is an inflammatory response of the skin, when its DNA is damaged by UV radiation. Since bacteria is only made up of a single cell, it relies on that cell’s DNA makeup to survive. If that cell is damaged and the DNA is disrupted, it’ll either kill the cell or leave it inactive.
A UV germicidal light is typically paired with a forced air system for greatest overall impact. The light is installed inside the return air duct, so you will not see it or be exposed to it. As air makes its way through the duct and passes the UV light, it is sanitized.