Replacement bulb for 18-watt, single lamp, return-air models. For use with UV100 ultraviolet air treatment system (models UV100A1000 and UV100E1043). Ultraviolet light penetrates microorganisms and breaks down molecular bonds causing cellular and/or genetic damage. Made from sodium-barium silicate and don't produce ozone. SnapLamp™ feature reduces costs by reusing bulb handle. Sealed unit prevents accidental installer / homeowner contact with high voltage and ultraviolet rays. Safe design prevents lamp from lighting unless base is correctly mounted on HVAC duct.