Lighting Levels

We all know the fairytale of Goldilocks and the Three Bears . While there are many variations, in the story’s popularised modern interpretation a little girl named Goldilocks goes for a walk in the forest, comes upon a house, enters, and finds three bowls of porridge: the first too hot; the next too cold; the third just right. Likewise, of the three beds she trials one is too hard, the next too soft, and the third so comfortable that she falls asleep. Since it wasn’t her house, let alone porridge or bed, things don’t work out too well for Goldilocks, but in the world of safety – where lighting should be neither too much nor too little – we should all aspire to the gold (-ilocks) standard.

When I was asked to write an article on lighting I was reminded of an incident where a plant manager wanted to ban sunglasses for employees working indoors. He said he found it absurd that workers could claim that there was a danger because of insufficient lighting, while wearing safety glasses tinted so heavily that they looked like they were blind. This set in motion a project for the safety manager to find a specification on exactly how dark safety glasses could be before the tinted lenses would constitute a hazard. Eventually it came down to an agreement between the plant manager and the Union representing workers, but I think it raises an interesting point: when does the lack of lighting, or too much lighting, constitute a hazard?

According to the law firm, Ellis Law Corporation: “Both indoor and outdoor workplaces can have lighting deficiencies that can lead to injuries. At an outdoor construction site, for example, employers are expected to set up high-powered, portable tower lights to give the workers enough lighting. In this scenario, the risk isn’t only that an employee may trip over equipment and fall, but also that an employee may make a mistake with heavy machinery. For example, an employee driving a backhoe without adequate lighting may strike and injure another worker. Or, a worker may slice off a finger with a circular saw because the work area isn’t properly illuminated.

Indoor workplaces can also be hazardous if there is a lighting deficiency. Employees may trip and fall in a darkened stairwell, storage closet, or copy room – or anywhere else that lacks sufficient lighting. These injuries are considered to be negligent and the victim is often entitled to damages for injuries, lost time at work, and for pain and suffering.”_¹

The lack of sufficient lighting is hazardous because it conceals many forms of hazards: from trip hazards to vermin and everywhere in between. Low light levels make it difficult to read warning labels and may lead to eye strain. Too much lighting, despite sounding like an alien concept, can also cause eye strain and even fatigue, so getting the right amount of light is key.

Recommended light levels

The National Optical Astronomy of Observatory (NOAO) has issued guidelines for light levels both for both indoor and outdoor Illuminance. According to NOAO, “Light level or illuminance, is the amount of light measured in a plane surface (or the total luminous flux incident on a surface, per unit area). The work plane is where the most important tasks in the room or space are performed.”²

Measuring light

NOAO has also issued guidelines for measuring light levels. Illuminance is measured in foot candles (ftcd, fc, fcd) or lux (in the metric SI system). A foot candle is actually one lumen of light density per square foot and one lux is one lumen per square metre:

• 1 lux = 1 lumen / square metre = 0.0001 phot = 0.0929 foot candle (ftcd, fcd)
• 1 phot = 1 lumen / square centimetre = 10000 lumens / sq metre = 10000 lux
• 1 foot candle (ftcd, fcd) = 1 lumen / sq ft = 10.752 lux)”

While this is all well and good, what are the optimal levels of illumination? The answer is the deeply unsatisfying: “it depends”. According to the NOAO, while it was once common practice to perform routine tasks with light levels in the range 100-300 lux, today the more common light level ranges from 500 – 1,000 lux; again depending on the activity being performed.

“For precision and detailed works, the light level may even approach 1,5002,000 lux. The table below is a guide for recommended light levels in different workspace.

Effectiveness of illumination

Generally, factors that affect the effectiveness of illumination are quantity and quality of light, amount of flicker, amount of glare, contrast and shadows. Each factor must be adjusted differently to optimise illumination in emergency, safety, operations, and security situations, for instance. Lighting standards also serve to address the plethora of other concerns associated with the design, placement, installation, and minimum energy requirements and efficient allocation of illumination in different locations with different purposes, as well as the efficiency, durability, cost, and maintainability.”³

“factors that affect the effectiveness of illumination are quantity and quality of light, amount of flicker, amount of glare, contrast and shadows”

I’d planned to change tack slightly at this point and look at the regulatory requirements for lighting; however, many of the studies I found were more interested in reducing excess lights, and by extension, electricity usage, in the furtherance of carbon reduction. Clearly a noble cause, but one that won’t necessarily stop me from falling in a pit. (Unless of course that pit and surrounding environment had previously been so incredibly over-illuminated that there were no shadows to differentiate the level change, thus meaning a reduction in excess lights would improve safety).

Essentially, we all know that working in dimly lit, gloomy environments is only going to create problems; whether that’s a lack of illumination of physical hazards, or the psychological impact of working somewhere nudging towards dark. But rather than make a potentially dull (pardon the pun) article any harder to read by piling into a list of standards and regulatory requirements, let’s instead see if I – drawing on my own decades of experience – can break this down into easy to digest chunks of information.

Illuminating semantics

The world over, a lot can be taken – rightly or wrongly – from our choice of language. The same word can have different connotations to people from neighbouring towns, let alone different cultures. Add into the mix an assumption of understanding, and you’ve a recipe for disaster – in or out of the workplace. When it comes to workplace safety, and lighting in particular, how can we help to lessen this little quandary? I’ll tell you: defining the language used to eliminate any confusion.

Adequate lighting

Workers need adequate lighting to get to and from their jobs. It’s okay, you can say it: words like “adequate” don’t mean much unless I tell you how “adequate” it has to be, and I am not going to bail out and say it depends. I think you know the answer, but, adequate lighting means lighting sufficient to illuminate the path enough so that hazards like slips, trips, and falls are negated. The obvious solution is to ensure that you yourself can see well enough in the existing light to traverse the path, confident that you will be able to see hazards.

Appropriate lighting

Workers need appropriate lighting to do their jobs safely, yet here again we have one of those tricky words. Let me again define exactly what I mean by “appropriate”. People need to see well enough to complete the tasks required of their jobs. The more detailed the task, the more light will be required to ensure the workers can not only do the job safely, but also that they don’t strain their eyes trying to puzzle out a task. A good way to determine whether or not the lighting of a work area is “appropriate” is to pay attention to how the workers are working. Are they squinting? Are they putting their faces close to their work to better see it? If the answer to either of these questions is yes, chances are good that there isn’t enough light in the work area.

Lighting versus illumination

While this article has preached the virtues of a goldilocks level of “just right” lighting, what’s actually important is illumination. All the lighting in the world doesn’t mean a thing if it fails to illuminate the surroundings. The word “illuminate” is an interesting word, because it has two very different meanings, it can mean to provide light (which of course is primarily the definition we will use in this context) but it can also mean to “make clear or provide enlightenment”.

In the context of safety, we can never lose sight (no pun intended) of the fact that our true goal in providing lighting in the work area is to provide the workers with the means to become aware of, and avoid, the sources of injury. So, for our purposes, it’s not about lumens and luxes, it’s about giving our workforce the tools to protect themselves from harm.

“all the lighting in the world doesn’t mean a thing if it fails to illuminate the surroundings”

Further hazards

As I was writing this I thought perhaps too much light is just as bad as not enough light. While on reflection that is definitely wrong, as insufficient light is certainly more likely to cause an injury, too much light can also create the following health and safety hazards.

Eyestrain

Both lighting that is too low and that is too high can cause eyestrain, yet low lighting is likely to cause eyestrain over a longer period of time than a blinding light shining down on a person.

Stress

Fact attack! Stress kills more people each year than hippopotami do, and those hog-faced brutes kill 500 people a year in Africa alone!! And to that end, if you are working in Africa it wouldn’t hurt to have sufficient lighting to see if a hippo is coming to kill you, but each to their own.

In all seriousness, lights that are too bright can cause stress which in turn causes all sorts of nasty illnesses, and increases the likelihood that a person will make more errors and exercise poorer judgement – with some of those errors and choices causing injuries. This is why a popular interrogation technique is to shine a bright light in a person’s face to induce stress.

Fatigue

Fatigue is more than just being tired. As I wrote in my article Dying to Make a Living in the September 2018 edition of OHS Professionals: “The link between stress and illness is scientifically well established. Recent research into fatigue and sleep deprivation has found strong links between worker fatigue and injuries, impaired judgment, and at-risk behaviour. In a 2007 study conducted by Vegso et al, researchers found an 88 percent increased risk of an incident for individuals working more than 64 hours a week. As employers try to do more work with fewer workers, workers are often forced to work while sleep deprived, ill and fatigued. As workers tire they make more mistakes and riskier choices, are less likely to comply with rules, and may become combative.”⁴

Temporary blindness

Temporary blindness occurs when a worker travels from an over-lit area into darkness, which is not atypical in night work endemic to construction sites and even some oil and gas locations. While this blindness is only temporary, many workers do not wait until their eyes have adjusted to the difference in the level of illumination and in that time they can be injured, sometimes seriously so.

“many workers do not wait until their eyes have adjusted to the difference in the level of illumination and in that time they can be injured”

Good to talk

But just how on earth do you decide how much light is not enough, and the level at which it all becomes too much? Well, just remember that you’re not alone in this. You have at your disposal one of the most powerful resources for determining whether or not you have sufficient lighting: the workers. Simply by having candid conversations with multiple workers and experimenting with lighting levels you can generally determine the appropriate illumination necessary for a worker to successfully perform his duties.

And what’s more, whether you find this a help or hindrance, depending on your working environment there may be no hard and fast rule throughout the day. Throughout the day you’re your lighting needs will change. At dawn, the levels of additional light required probably won’t be the same as they are at noon, and the day shift will most certainly have different illumination needs than the night shift. Unless you’re working above the article circle, in which case needs will change seasonally between perpetual sunlight and inescapable darkness. The prudent move is to have lights that you can turn on and off and adjust as the environment and workers’ needs change. This will also involve educating the workers on when they should turn a light on or off.

In the final estimation, and how it directly applies to you, you may have to fine tune much of this on your own. Or preferably, if you find yourself in need of definitive answers about lighting, engage the services of an engineer or architect who specialises in lighting. It’s for this reason that I deliberately didn’t include the formula for calculating the exact number of lumens and luxes – if your needs are that great you should seek a specialist professional. Should you be desperate to have a go yourself, the formulas are available online⁵ should you choose to go down that route.

References

2 ellisinjurylaw.com/premises/3-wayspoor-lighting-can-cause-an-injury/

3 www.noao.edu/education/QLTkit/ ACTIVITY_Documents/Safety/ LightLevels_outdoor+indoor.pdf

4 www.noao.edu/education/QLTkit/ ACTIVITY_Documents/Safety/ LightLevels_outdoor+indoor.pdf

5 www.aihs.org.au/sites/default/files/ OHSProSeptFinal.pdf

6 www.bannerengineering.com/my/en/ company/expert-insights/lux-lumenscalculator.html