UGR19 stands for Unified Glare Rating of 19 or less, which is a parameter of how bright a luminaire is in a sample room layout, and is particularly important in office spaces where workers have to spend many hours a day and would be using display terminals for a large proportion of that time.
The higher the UGR number the higher the glare from the luminaire and the increased discomfort for office workers. The glare can cause health and safety issues and welfare problems such as headaches, migraines and eyesight issues. The light fitting alone cannot be UGR19 compliant as it is not a characteristic of a luminaire but is a measure of how it performs in a physical space. Luminaires can be manufactured to reduce glare and these low glare light fittings help support a UGR19 compliant lighting scheme.