People stay in indoor environment for most of the day. Characteristics of light in indoor environment are much different than that of natural outdoor environment. On the other hand people do not stop activities after sunset. The artificial lighting has therefore impact on their well-being (see also the visual and non-visual aspects of light in Chapter 3). The needed artificial light has to be provided in energy efficient and environmentally conscious way. It is important to search for the technological solutions which meet human needs with the lowest impact on the environment during operation, when most of the impacts take place. The environmental impacts also include production
and disposal of lamps, and related materials