In 1903, Niels Finsen won the Nobel Prize in Medicine for his use of ultraviolet light in the treatment of tuberculosis. Since then, ultraviolet lights have been widely adapted for all kinds of uses: sterilizing hospitals, sterilizing water, germicidal lamps in food establishments, and even curing nail polish faster. If UV light is so effective, how can it be applied to improving indoor air quality for residential HVAC systems? Will it kill mold and bacteria in HVAC systems? Yes, but you need to understand the priorities of indoor air quality and the types of UV lights available for residential HVAC systems.