Lighting from an occupational safety perspective – what operators and facility managers should know

Workplace stress has many different causes. One of the most prominent is poor light. Inadequate lighting can lead to headaches, tiredness and irritability. Employees' performance decreases if poor lighting reduces their concentration span and makes them less able to focus. Accidents are almost inevitable at this point.

While research into the non-visual effects of lighting solutions in work areas is still at an incipient stage, current regulations on workplace lighting have so far concentrated on the direct visual effects: Hazards must be illuminated so that they are clearly visible for the people in a plant. Falls can be prevented by using suitable lighting to ensure that trip hazards can be seen. So install light fittings and you're done? It's not quite that simple. On the one hand, the applicable regulations and standards must be complied with and, on the other hand, operators are wasting valuable potential by not planning lighting optimally.

The most important regulations on lighting work areas include

• German Occupational Safety and Health Act
• Technical regulations on workplaces (ASR)
• Workplace Ordinance (ArbStättV)
• "Lighting" accident prevention regulation (BGV A8)
• Regulations for good visibility specified by the employer's liability insurance association (BGR)
• Technical regulations on hazardous substances

The publication of DIN SPEC 67600 "Biologically Effective Illumination – Design Guidelines" in 2013 caused quite a stir among occupational safety experts. This is because the document contained detailed information on how light installations – including those at workplaces – could be specifically used to achieve non-visual effects. Occupational safety experts criticised this report because it provides very specific recommendations that are not based on actual scientific findings, as this knowledge is still not available to this day. There is no dispute that light has non-visual effects on humans. And everyone has probably already experienced at first hand how light can affect their own well-being and mood. Insufficient or uneven lighting affects people's performance and motivation, and increases fatigue.

A great deal of research has been conducted into the effects of light on seasonal affective disorder (SAD). In the dark winter months, some people experience low mood and lethargy because the lack of daylight affects the production of hormones and neurotransmitters. With fewer hours of daylight, levels of the sleep hormone Melatonin decrease more slowly in the morning, while it takes longer for this hormone to be released as well. What's more, levels of the neurotransmitter Serotonin, also known as the "happiness hormone", in the brain are also lower over the winter.

In 2001, neurologists from Jefferson Medical College in Philadelphia (USA) achieved a breakthrough in research into the non-visual effects of light on humans. They discovered a new photoreceptor in the retina which helps explain how light controls the human biological clock. The researchers were able to prove that this photoreceptor controls Melatonin production and responds to short wavelength from visible spectrum, the blue light in particular.

Nowadays this finding is frequently applied to computer monitors and screens on mobile phones and tablets, for example. "Eye Comfort" or "Night Shift" functions can be used to reduce blue light, for example in the evening, so that the production of Melatonin is not affected. This is important to keep our biological clock in sync with the natural day-night rhythm.

The Federal Institute for Occupational Safety and Health (BAuA) conducted an interesting experiment in 2015, where 18 participants were exposed to different lighting conditions in the morning and evening. The researchers discovered that blue light in the morning woke participants up and improved their reaction time. What's more, these participants still felt more awake and productive in the evening compared to the control group that was exposed to dimmed incandescent lighting in the morning. From the BAuA's point of view, "there is evidence to assume that under daily life situations lighting conditions are often not sufficient to synchronize the internal clock to the external 24-h rhythm" and that "the lighting during the day can significantly contribute to our alertness and performance". Being exposed to light at the wrong time could therefore cause desynchronisation of the internal clock, as is observed among shift workers. The possible consequences include difficulty concentrating, altered metabolic function and even cardiovascular disease.

However, the research carried out so far does not allow any generally applicable quantitative statements to be made regarding the non-visual effects of light. In order to do so, cause-effect findings would be required so that numerical values could be determined for illuminance or colour temperature. However, one thing is clear: The day-night cycle that is also known by the technical term "circadian rhythm" is relevant to occupational safety. By analysing 3000 industrial incidents, experts from the BAuA were able to prove that the occurrence of accidents reflects daily and seasonal changes in daylight. This is one of the reasons why the Commission for Occupational Health and Safety and Standardization (KAN) once again reinforced in a position paper published in September 2022 that occupational safety requirements are impacted by the non-visual effects of artificial lighting and must be taken into consideration in standardisation plans.

So what does this mean for lighting in industrial plants? First of all, the latest findings clearly show how important it is to plan lighting. For this purpose, German Social Accident Insurance (DGUV) recommends:

• Using as much daylight as possible and positioning workstations close to windows where possible.
• Where little or no daylight is available, bright artificial lighting or light sources containing a lot of blue light should additionally be used during the day.
• Bright light and light sources containing a lot of blue light should be avoided in the evening – at the latest two hours before going to sleep.
• You should also avoid looking directly at the light source in the evening.
• It is recommended that employees take their breaks outside where possible.
• When working the late shift or night shift, bright light or light sources containing a lot of blue light should generally be avoided.
• Light sources that are not needed should also be switched off or dimmed at night.
• For activities involving particular risks, bright light or light sources containing a lot of blue light promote alertness and focus – but carrying out a risk assessment beforehand is crucial here.

To enable new findings to be transferred to practice in existing plants, the German Occupational Safety and Health Act obligates employers to regularly review measures relating to the health and safety of employees and update them as circumstances change. The German Workplace Ordinance and the "Risk assessment" technical rules for workplaces (ASR V3) specify how this review should be carried out.

In the past, there were relatively few options for lighting in industrial plants. The limited colour spectrum of fluorescent tubes or even sodium-vapour lamps and the associated poor colour saturation in particular lead to visibility problems: Colourful markings – for example on safety equipment – are often much harder to identify in this artificial light compared to daylight.

Against this backdrop, LED lighting concepts open up a vast array of promising options. LEDs make it possible to specifically use the wavelength of the light emission and also to meet specific requirements, in addition to providing extremely energy-efficient general lighting with a spectrum similar to that of daylight. One example from industry is the identification of emergency showers and eyewash stations, for which green light is recommended. People suffering burns, including chemical burns, must be able to locate the emergency shower as quickly as possible.

Unlike filtered fluorescent lamps, which have a limited colour saturation due to their high white light content, LEDs achieve high colour saturation. This makes it much easier to detect the colour. What's more, LEDs last far longer than conventional linear luminaires with fluorescent tubes. This is because these luminaires lose their brightness relatively quickly over their service life, meaning that their ability to function as a visual signal continuously decreases.

A promising solution here is the combination of colour diodes and a white light LED in a linear luminaire (EXLUX 6002). On the one hand, this provides a green visual signal so that the emergency shower can be located quickly, while its middle part consisting of a white light LED makes it more visible from a distance and ensures good visibility at the station itself. Other examples include blue lighting for fire extinguisher stations or LED lighting solutions with more yellow in the light spectrum, which attract fewer animals to offshore platforms. What's more, connecting and disconnecting light fields creates a visual boundary between different process areas and is a highly effective way to designate an evacuation route.