Whether in industrial or office settings, proper lighting makes all work tasks easier and safer. People receive about 85 percent of their information through their sense of sight.
Appropriate lighting, without glare or shadows, can reduce eye fatigue and headaches. It highlights moving machinery and other safety hazards. It also reduces the chance of accidents and injuries from ‘momentary blindness’ while the eyes adjust to brighter or darker surroundings.
The ability to see at work depends not only on lighting but also on:
- The time to focus on an object; fast moving objects are hard to see
- The size of an object; very small objects are hard to see
- Brightness; too much or too little reflected light makes objects hard to see
- Contrast between an object and its immediate background; too little contrast makes it hard to distinguish an object from the background
- Insufficient light – not enough light for the need
- Glare – too much light for the need
- Improper contrast
- Poorly distributed light
- Flicker Poor lighting can cause several problems such as:
- Misjudgment of the position, shape or speed of an object can lead to accidents and injury
- Poor lighting can affect the quality of work, particularly in a situation where precision is required, and overall productivity
- Poor lighting can be a health hazard – too much or too little light strains eyes and may cause eye irritation and headaches
How much daylight reaches inside a building depends on the amount and direction of sunlight, cloud cover, local terrain, and the season. The size, orientation and cleanliness of the windows is also important. The amount of daylight entering the workplace can be controlled with tinted glass, window blinds, curtains, and awnings. Daylight is desirable in the workplace providing it does not cause glare or make the work area too bright. Remember, not enough light can also be a problem so even in workplaces where daylight is available, it is essential to have a good electric lighting system.
The amount of light, the colour of the light itself and the colour that objects appear vary with the type of electric lighting. The lighting must match the workplace and the task.
There are three basic types of lighting:
- Local, or task
General lighting provides fairly uniform lighting. An example would be ceiling fixtures that light up large areas. Localised-general lighting uses overhead fixtures in addition to ceiling fixtures to increase lighting levels for particular tasks. Local, or task lighting increases light levels over the work and immediate surroundings. Local lighting often allows the user to adjust and control lighting and provides flexibility for each user.
Different types of light fixtures
The complete lighting unit (also called the light fixture, or luminaires) controls and distributes the light. Various types of light fixtures are designed to distribute light in different ways. These fixtures are known as:
No single type of light fixture is appropriate in every situation. The amount and quality of lighting required for a particular workstation or task will determine which light fixture is most suitable. Direct light fixtures project 90 to 100 percent of their light downward towards the work area. Direct lighting tends to create shadows. Direct-indirect light fixtures distribute light equally upwards and downwards. They reflect light off the ceiling and other room surfaces. Little light is emitted horizontally, meaning direct glare is often reduced. They are usually used in ‘clean’ manufacturing areas.
Indirect light fixtures distribute 90 to 100 percent of the light upward. The ceiling and upper walls must be clean and highly reflective to allow the light to reach the work area. They provide the most even illumination of all the types of fixtures and the least direct glare. Indirect light fixtures are usually used in offices. Shielded light fixtures use diffusers, lenses and louvers to cover bulbs from direct view, thereby helping to prevent glare and distribute light.
- Diffusers are translucent or semi-transparent covers made usually of glass or plastic. They are used on the bottom or sides of light fixtures to control brightness
- Lenses are clear or transparent glass, or plastic covers. The lens design incorporates prisms and flutes to distribute light in specific ways
- Louvers are baffles that shield the bulb from view and reflect light. The baffles can be contoured to control light and decrease brightness.
Parabolic louvers are specially shaped grids that concentrate and distribute light LED (light-emitting diode) bulbs are now on the market. They use 85% less energy and last up to 20 years longer. LED lighting presents a new, more environmentally friendly option. It’s long lasting and can save you money over an extended period. These lights are heavier than other lighting options, and the bulb is on average a little taller than a standard light bulb; however, the base can fit in standard light sockets. These lights will keep going long after incandescent and CFLs (compact fluorescent lamps) would have stopped working, and they’ll save you money on your electrical bill. They are more expensive but the return on investment is huge.
The incandescent light bulb has been the standard lighting option for nearly 100 years. In recent decades, the CFL has gained popularity because it’s more energy efficient and lasts longer. The bulb contains mercury, however, and takes a while to shine at its brightest – and is expensive for disposal. On average, about a dozen watts from energy efficient LED bulbs provides the same amount of light as a 60-watt incandescent. This means you save on electricity without scrimping on the amount of light you have.
LED light bulbs – what to look for
When you’re shopping for an LED light bulb, it’s important to find one that provides the amount of light you need, as well as the colour of light you like. You’ll also want to consider how the light emits from the bulb, and the dimension of the bulb and base.
- Features – A standard 60-watt incandescent bulb puts off about 800 lumens. The more lumens, the brighter the light is. LED light bulbs provide many lumens for few watts compared to incandescent bulbs. Since this is the case, it’s better to find a bulb that has low wattage but high lumens because it will save you on your energy bill. You also want to find an LED light bulb that offers a long lifespan. Most offer between 25,000 and 50,000 hours of light.
- Design – The dimensions and weight of LED bulbs are not the same as a standard incandescent bulb. LED light bulbs are on average a quarter of an inch taller. The average diameter of these LED lights is similar to that of incandescent bulbs, but varies depending on the model. LED lights are also heavier than incandescent bulbs, so you’ll want to be sure that your light fixture can support the extra weight. Most LED light bulbs can’t be fully enclosed in a light fixture because heat decreases the life of the light bulb. If you plan to use your LED light bulbs outside, you’ll first want to verify that they can withstand damp outdoor conditions. If you want to dim your lights with an LED light bulb, you’ll need to have one that the manufacturer has specifically designed to perform as a dimmer. The beam spread is another thing to consider. While incandescent lights put off light in all directions, LED lighting typically sends its light in one direction. The best LED light bulbs that are comparable to 60-watt incandescent bulbs distribute the light around the bulb as well as from the top.
- Help and support – Chances are you won’t need to be in contact much with the manufacturer to use your light bulbs. Having a practical return policy and warranty is important, though, since these light bulbs cost more than incandescent and CFLs. A good LED light bulb should come with at least a three to five year warranty.
Test and correct poor lighting problems
To detect insufficient light, try the following:
- Wipe light fixtures with a damp cloth to check for cleanliness; an evenly deposited film of dust is hard to detect by sight alone
- Measure the average illumination throughout the workplace; compare this to the recommended levels
- Look for shadows, especially over work areas and on stairways
- Ask workers if they suffer from eye strain or squint to see
Workers should sit in their normal working positions during measurement to give you accurate results. To correct insufficient light:
- Replace bulbs on a regular schedule. Old bulbs give less light than new ones so replace them before they burn out. Follow manufacturers’ instructions
- Clean light fixtures regularly. Dirt on light fixtures reduces the amount of light given off. Light fixtures with open tops allow air currents to move dust up through the fixture so dust and dirt do not accumulate on the fixture
- Add more light fixtures in appropriate places
- Paint walls and ceilings light colours so light can be reflected
- Use more reflected light and local lighting to eliminate shadows; for example, a covered light mounted under a transparent guard on a grinding wheel provides the added light needed to clearly see the task
- Do not position work station with light fixture directly behind worker
What should you know about glare?
Glare is a common lighting problem. Glare is what happens when a bright light source or reflection interferes with how you are ‘seeing’ an object. In most cases, your eyes will adapt to the brightest level of light. When this adaptation happens, it becomes harder to see the details in the duller or darker areas of the work space (even though they are actually sufficiently lit). Glare can cause annoyance and discomfort, and can actually decrease a person’s ability to see.
How do you detect glare?
There are several ways to find sources of glare:
- When in your normal working position, look at a distant object at eye level. Block the light ‘path’ from the fixtures with a book or cardboard. If the distant object is now easier to see, the light fixtures are probably producing glare.
- To detect reflected glare, look at the task from your normal working position. Block the light falling on it from the front or above. If details are now easier to see, reflections are a problem.
- Place a small mirror face up on the work surface. The mirror reflects light from above, the light fixture is responsible for glare.
- Look for shiny objects that reflect light. Glass in picture frames, glossy table tops and VDT screens are common examples.
- Ask workers if they experience sore or tired eyes, headaches, or if they need to squint to see.
To correct glare, try:
- Using several small low-intensity light fixtures rather than one large high-intensity light fixture
- Using light fixtures that diffuse or concentrate light well; indirect light fixtures or direct light fixtures with parabolic louvres are two possibilities
- Covering bare bulbs with louvres, lenses or other devices to control light
- Increasing the brightness of the area around the glare source
- Using adjustable local lighting with brightness controls
- Positioning light fixtures to reduce reflected light that is directed toward the eyes
- Using low gloss paper or apply flat or semi-gloss paint and matt finishes on ‘offending’ surfaces. Remove highly polished and shiny objects
- Keeping general lighting at recommended levels
- Positioning the work station so that windows and fluorescent light tubes are parallel to the worker’s line of sight
- Do not position the work station so that light fixtures are to the front or directly overhead
Poorly distributed light?
When light is poorly distributed, parts of the ceiling and general surroundings will seem dark and gloomy. Substantial differences in light levels force your eyes to readjust when moving from one light level to another. Workers may find it difficult or impossible to see properly.
You can detect poorly distributed light by:
- Looking for dark areas and uneven lighting
- Using a light meter to check the illumination at various points throughout the workplace. With uniform general lighting, the minimum reading should not be less than two-thirds of the average value
Correct for poorly distributed light by:
- Supplementing or replacing light fixtures with ones that distribute some light upwards
- Painting ceiling and walls in light colours that reflect light
- Cleaning ceilings, walls and light fixtures
A complete lighting survey may be needed to identify and solve more subtle or complicated problems. A complete lighting survey requires complex equipment and practical experience. A complete basic lighting survey includes the following:
- Illuminance – Illuminance doesn’t only make the city safe: it is also relevant for industrial work places. The right direction and strength of indoor lighting enables quick and accurate work, safely in vast and often largely windowless buildings. The same principles apply to lighting in industry and production as to working places in the service industry. The individual must feel well. Illuminance is the amount of light falling on a surface. The unit of measurement is lux (or lumens per square metre = 10.76 foot candles, fc). A light meter is used to measure it. Readings are taken from several angles and positions.
- Luminance – Luminance is the amount of light reflected from a surface. The unit of measurement is candela per square metre (equals 0.29 foot-lamberts). An illuminance meter is used to measure it. Several measurements are made and averaged. Luminance tables are consulted for reference values.
- Contrast – This is the relationship between the brightness of an object and its background. A luminance meter is used to measure it. The following formula is used to calculate contrast and provides a number between 0 and 1. The average contrast should be above 0.5:
- Reflectance – This is the ratio of light falling on a surface to the light reflected from a surface, expressed as a percentage. A light meter is used to measure it. Reflectance can also be measured using a reflectometer or by comparing the surface of interest with colour chips of known reflectance.
The cost factor of industrial lighting is one that weighs heavily on employers, particularly in these troubled economic times. Too often saving on the lighting of industrial workplaces means compromising on safety and reducing productivity due to poorer working conditions.
Published: 01st Sep 2012 in Health and Safety International