Ultraviolet germicidal irradiation (UVGI), also called ultraviolet germicidal energy, is a technology using light as a disinfectant. The entire UV spectrum can kill or inactivate microorganisms, but UVC energy provides the most germicidal effect. Most contemporary UVGI lamps produce UVC energy that damages the nucleic acids and proteins of pathogens, making them inactive and unable to transmit infection. UVGI units are most effective in residential ducts or air handling units.