Learning Center Light Bulb Types: Speciality Germicidal What are they? A germicidal light bulb or lamp is designed to use a combination of special phosphors and a quartz glass envelope for the process of eliminating germs and/or the creation of ozone. They come in a variety of wattages, voltages, sizes, and base types. They produce little if any visible light and are designed primarily for the purpose of sterilization or ozone creation. How do they work? Germicidal lamps come in two main types, low pressure and medium pressure. Low pressure is the more common of the two types, and they are almost always fluorescent lamps. They differ from regular fluorescent lamps in two primary ways: The glass envelope or tube is made from fused quartz, and there is no phosphor in the tube. The lack of phosphor allows ultraviolet light in the short-wave UV-C range to leave the lamp unaltered. In germicidal applications, they function by creating ultraviolet light in a specific range as a mutagen that is effective at killing bacteria by disrupting its DNA structure. High pressure lamps work the same way, but generally create a higher intensity output in a wider range of UV light. These are often used in applications such as water purification, where a large area needs to be disinfected by each lamp. Where are they used? Germicidal lamps are used in a variety of applications where disinfection is the primary concern, such as water and air purification, food and beverage protection, and sterilization of sensitive tools such as medical instruments. It is important to note that the UV range used in most germicidal bulbs is harmful to both skin and eyes, and should not be used in any fixture or application that was not designed specifically to prevent exposure to humans or animals.