It's no mystery that cleanrooms present numerous challenges to designers who specify lighting systems. Cleanroom lighting will vary depending on the room's use, its classification and ceiling air supply configuration. In an ideal situation, lighting systems should provide good visibility and be designed with contamination control issues—electromagnetic field generation and cleanability—in mind. But before that can be achieved, a thorough examination of the basic fundamentals, illumination requirements, available styles and fixture construction must be undertaken. Considering the fundamentals, the purpose of lighting systems is to provide visibility. Issues such as initial costs, energy, and maintenance costs typically contribute to lighting design decisions in most facilities, but for a cleanroom facility, the cost of lighting fixtures typically represents less than 1 percent of the total budget. Energy costs associated with lighting are usually minimal compared to the cleanroom HVAC and process equipment power demands. The focus in cleanroom lighting then becomes proper illumination, coordination with air supply systems and reduction of contamination for the unique environments and processes that reside in the space.