We just published a paper discussing future directions for ultraviolet germicidal irradiation (UVGI). Ultraviolet germicidal irradiation for air disinfection applications has relied on low-pressure mercury vapor lamps for decades. New design requirements have generated the need for alternatives in some uses. This paper describes the current state of UVGI technology and describes future directions for technology development, including the use of lamps produced from non-toxic materials and light-emitting diode lamps. Important applications are discussed such as the use of ultraviolet germicidal lamps in developing countries, in heating, ventilating and air-conditioning systems to improve energy efficiency and indoor air quality, and for whole room disinfection.