Hospitals are high exposure environments where transmission of infectious diseases is a large concern. To prevent this Ultraviolet Germicidal Irradiation (UVGI) systems are used as an engineering control. A common application is upper-room irradiation for which germicidal lamps are suspended from ceilings/ attached to walls, while the bottom of the lamps are shielded to direct radiation. The principle is to maximize UV radiation exposure to airborne microorganisms in the upper part of the room while minimizing radiation exposure to patients in the lower part.