Office illumination
It has been known for a long time that proper illumination is one of the main factors for enhancing of concentration and well-being of persons working behind a desk. It is especially important if we spend many hours a day in front of a computer.
Therefore, it is very important to design the illumination in a way, which would make us feel that our eyes are not fatigued, and we feel good in the room we work in.
If it is possible, we should use the daylight as long as possible during the day. Rays of sun are namely most friendly for our eyes and activate our body to work in a natural way.
This is why we feel more motivated to work and less sluggish in a room with access to daylight than in a room with artificial light only – artificial light is, in addition, often improperly designed (unfortunately, there are many offices of such kind).
In afternoons and evenings, of course, we use properly designed artificial illumination, which should include a main source of light and a concentrated source of spot light (in most cases, these are small desktop lamps).
The main source of light
If we spend 8 hours a day or even more in the given room, the choice of type of light for its illumination is not meaningless. Even if we do not pay attention to this fact and will use a randomly chosen and randomly arranged source of light, it will influence our health anyway (if an improper type of illumination is chosen, this influence will definitely be unfavourable).
It is a good solution, successfully applied in many offices, to use fluorescent lamps. They provide an even illumination for the room and save energy.
Note: fluorescent lamps of good quality must be used. The present European norms for illumination (EN 12464-1) recommend namely that premises where people stay for a long period should be equipped with fluorescent lamps with the colour-rendering index (Ra) of more than 80.
Yet, many offices are still equipped with lamps of the old type, with a very low Ra index. Items and persons illuminated by these lamps look cold and pale. It results in a relatively quick effect of eye fatigue and has an unfavourable influence on our well-being.
Thinking about our health
The market offers easily available fluorescent lamps, which produce good and healthy light with Ra amounting to 85. In such illumination, the environment seems to be fresh and lively, which clearly contributes to our better mood.
Such types of fluorescent lamps are also available in versions producing “warmer” or “cooler” light. This way, depending on the decoration of the room and our preferences, we can decide to install adequate lamps in our office.
At the same time, it is more favourable to use fluorescent lamps with a cooler colour “temperature”, closer to the daylight, in rooms with more or less limited access to the daylight. This way, we will stay in good shape all day long.
However, if the room we work in is illuminated with traditional bulbs, we should remember that siliconised bulbs are a better solution, as they provide for milder and less blinding light.
Desktop illumination
A properly chosen desktop lamp is – apart from the computer and the desk – one of the most important parts of equipment used by the given employee. It reduces eye fatigue and is helpful in case of precise activities.
We recommend choosing of a light, portable lamp with a long arm, which is easily adjustable. Such a lamp should be placed on the side of the working person in such a way that the light reflected from the monitor or the surface of the desk is not dazzling for the eyes.
In case of right-handed persons, the lamp should be placed on the left side, and in case of left-handed persons – on the right side of the desk.
Little halogen lamps function well as desktop lamps. Halogen bulbs, designed for such lamps, produce light with a nice and attractive colour, and also last even five times longer than usual bulbs.
When customers come
If we receive also customers, contractors and guests in our office, we certainly should think about additional, typically decorative illumination as well.
A proper mood in the room can be achieved, among other things, through use of light accents, such as:
• side illumination (coloured light, lamps in interesting shapes)
• illumination of recesses (solutions as above)
• illumination of decorative elements, such as paintings on the walls or sculptures standing on the floor, from below
• illumination of plants from below
In this case, illumination using modern, “brilliant” light of halogen bulbs is often applied.
Lamps producing light through LED’s are new on the market. They can replace both usual bulbs and halogen bulbs (for 230 V). The LED’s used in these lamps are extremely lasting and do not emit high temperature, as opposed to halogen lamps.
Types of illumination
What industry experts professionally call sources of lights is simply a type of illumination for usual people. Therefore, we mean here bulbs, fluorescent lamps, glow tubes, halogens, discharge lamps, etc.
The basic distribution of sources of light results from the way in which the light is induced in them. We therefore distinguish the following types:
• bulbs (filament lamps) – the light comes from heated filament (a thin metal wire), glowing in a glass vacuous bulb or in a bulb filled with an adequate gas (e.g. a noble one) or a mixture of gases
• discharge lamps – the light comes from electrical discharges, occurring in adequate gas mixtures
• LED’s (electroluminescent) – the light comes from effects at the atom level, occurring in semiconductors (electroluminescence)
Bulbs
Bulbs are the oldest and the most popular sources of light. They function due to a filament heated up to a high temperature, emitting heat and light.
Only approx. 5% of electrical energy supplied is transformed into light, and the whole remaining energy is returned to the environment in form of heat.
Traditional bulbs are vacuous lamps. They produce nice-looking, “warm” light. Their durability is specified as approx. 1,000 working hours. During this time, the tungsten wire placed in the bulb evaporates gradually and its volume is reduced. Finally, the filament is burnt out.
Bulbs that are more modern are filled with noble gases or with halogen pairs (i.e. compounds of elements like chlorine, bromine, iodine).
Modern bulbs are e.g.:
• krypton bulbs – filled with krypton, produce by 10% of light more than usual bulbs and make it possible to achieve uniformly white colour of the light; they are perfectly suitable for illumination of large areas or working places, their walls are covered with a special layer, which reduces the effect of glare
• halogen bulbs – contain halogen pairs, they are by approx. 100% brighter than traditional bulbs, whereas they consume approx. twice less energy and can be powered by mains voltage or low voltage; in modern halogens, a coating limiting undesirable UV radiation is applied.
Discharge lamps
In discharge lamps, processes inducing light occur in the glower, i.e. a hermetically sealed, transparent, short tube, with electrodes fused in its ends. Due to discharges between them, the substance filling the glower starts glowing.
In order to illuminate, discharge lamps require special devices for ignition (glow starters) and for stabilisation of the current value (stabilisers).
Stabilisers ensure that discharge lamps do not flicker during switching on and work.
Discharge lamps are used in all places where durability and a high luminous flux are required, i.e. at all kinds of displays and exhibitions, on stadiums and in sports halls, in greenhouses and orangeries, in offices, industrial buildings and outside of buildings.
Discharge lamps are divided into the following types, depending on the substance filling the glower:
• mercury discharge lamps – contain mercury vapour; depending on the partial pressure of the mercury vapours in the glower, low- and high-pressure lamps are available; the most popular type of a low-pressure mercury discharge lamp is a fluorescent lamp, commonly called glow tube; there are also miniaturised fluorescent lamps available, called compact lamps.
In comparison with bulbs, fluorescent lamps consume much less energy and are more durable – on average, a fluorescent lamp consumes approx. 20% of the energy needed for a comparable bulb and functions approx. 12,000 hours long (a bulb can work approx. 1,000 hours long).
High-pressure mercury discharge lamps are also used e.g. in solariums or in places where artificial light is supposed to “act as” natural light, as their illumination is similar to the sunlight.
• sodium discharge lamps – in these lamps, sodium atoms are induced; the type of sodium radiation makes the sodium discharge lamps achieve exceptionally high illumination efficiency (high-pressure sodium discharge lamps are the most efficient ones among all high-pressure discharge lamps).
Sodium discharge lamps are very durable, so they are applied as economical sources of light for general illumination.
• Metal halide lamps – their name comes from halides (metal iodides); they are characterised by a very good colour of light and considerable light efficiency.
For the same illumination effect, a metal halide lamp with more than twice lower power is needed in comparison with a traditional bulb. The light produced by these lamps – as it is a kind of spotlight – can be very easily controlled.
LED’s
In case of LED’s, the light comes from energy conversions on the atom level, occurring in semiconductors, such as e.g. silicon carbide.
Due to the properties of semiconductors, atoms induced by electric current behave in a way resulting in production of light. This process is called electroluminescence.
LED’s are sources of light with high efficiency, but they emit monochromatic light, i.e. in one colour: green, blue, red. The colour of the light depends on the voltage of the current inducing the LED.
LED’s are most commonly used as indicating lights – thus, they are mainly used in small lamps indicating the condition of devices – and as alarm illumination.
We can also find them mainly in local light fittings in busses or planes and as accentuating light (in garden fittings, accentuating stairs, in fittings for shelves and cabinets in stores as well as in fittings with coloured illumination effects).
Motion detectors and twilight sensors
We can accordingly control the light in office premises and outside of the office, achieving the effect of lighting up and putting out of the illumination at adequate points in time and in adequate conditions as specified by us.
This way, we can – in spite of some costs borne in the beginning – save quite much and avoid unnecessary use of light, e.g. when everyone has already left the company, and lights are still on.
Motion detectors and twilight sensors are used for control of the illumination. As mentioned above, in spite of some initial costs related to their purchase and installation, it is a very convenient solution.
Detectors of motion and presence in a room control switching on and off the light, and more advanced devices (e.g. connected with systems included in installations of an intelligent building) can be used for light adjustment as well: dimming and brightening up or even changing of the colour.
Standard motion detectors react to a change in infrared rays, emitted by every living being. If a person comes near the detector, light is switched on, and when he/she leaves – the light goes out.
Twilight sensors work in a similar way.
It is their task to send impulses to the light control system when the light intensity falls to reach some specific, previously set values.
Twilight sensors can work outside; then, they react to changes of the natural light (sunlight). They can be installed inside buildings as well – then, they react to changes of the light intensity in the given room.
When the threshold value of the intensity is exceeded (it can be a permanent value or a value programmed by the user), the sensor puts the light on or out.
It is very useful in office premises, because people working in the rooms often fail to assess the intensity of light in the room, or – being busy with their work – forget about switching on the light at an appropriate time. It will cause unnecessary eye fatigue.
Do you know that?
Almost complete darkness corresponds to 5 luxes, and maximum brightness – to 1,000 luxes.
At the same time, even if the light intensity were increased above 1,000 luxes, human eye would not perceive it anyway.
Lux (lx) – a unit of light intensity in the SI System of Units. It stands for intensity of light produced by a flux of 1 lumen on 1 square metre.
