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When it comes to workplace safety, there are few aspects as universally essential and important as having high-quality lighting from a professional online lighting supplier with expert knowledge.
An obvious issue is that poor quality lighting makes workplace hazards more difficult to see and therefore avoid, poor lighting can cause a variety of health issues such as migraines, headaches, eyestrain and certain symptoms according to the Health and Safety Executive are associated with SBS (Sick Building Syndrome).
Many hazards can be found in a typical workplace including glare from lighting. It is simultaneously one of the most problematic and most difficult to measure. This has led to the development of the universal glare ratio (UGR) to help develop a guide to a practical solution.
The Two Types of Glare
Glare can affect people in different ways. These should be minimised as much as possible.
Disability glare, sometimes known as dazzle, is where a lighting source shines so intensely it impairs the vision of other objects, such as when a torch is directly shined into your eyes and you cannot see anything else.
By contrast, discomfort glare does not impair vision directly, but can feel particularly uncomfortable, and is usually caused by a contrast between different types of light, such as ambient lights, ceiling lights and a computer screen.
With these types of glare there are two directions of origination. Direct glare is typically caused by a bright light source directly within a field of vision. Indirect glare typically reflects off a reflecting surface first.
Because the most common type of glare caused by artificial lighting is discomfort glare, most lighting designers will mean discomfort glare when they refer to glare, including in the UGR.
What Is The UGR?
Developed by the International Commission on Illumination (CIE), the UGR is a logarithmic calculation of the glare of all visible lamps divided by the background luminance.
The formula is found in the document CIE 117-1995 and takes into account not only the intensity of individual light fittings but also how they compare to the light intensity perception in the surrounding area.
The calculation typically provides a result from 5-40, with higher numbers being more uncomfortable and any result higher than 30 causing particularly noticeable distraction and discomfort.
It is essential to note that the UGR is not a ratio that is used to measure an individual light, and any lighting fixtures that use UGR as a selling point often assume a “standard” height and space for the intended lighting environment.
For most workplace environments, a lighting installation must achieve a UGR of 19 or below in order to qualify as low glare, and 19 is typically seen as the limit for most office-based workplaces and computer-based work.
A more comprehensive list of recommended workplace UGR ratings can be found in BS EN 12461-1:2021.
In order to design and reach a certain UGR, a lighting designer would use a dedicated software package such as Dialux, which allows for complex lighting concept planning and accurate simulation of light behaviour, as well as calculating different lighting positions and the effects of different lighting elements.