Ultraviolet lamps can be easily added to an existing forced air system. Lamps can be installed either in the main supply or return duct of a central heating or air system. The germicidal effects of UV light cause photochemical damage to DNA and RNA within microorganisms. UV technology is widely used in hospitals, pharmacies, and commercial kitchens to kill airborne and surface microorganisms like mold and bacteria. Now homeowners can benefit from UV products, too.