Light Meter

Light plays a major role in most living organisms and in the operation of certain chemical processes. The light radiation occurring at a particular location can be described by the values for brightness determined with a light meter and by the colour of light. However, the term light meter or photometer is used to describe not only the devices for measuring the properties of light, but also the devices that use light sensors to determine quantities that affect the light transmission of the substance under inspection. In the following text, only the devices used to determine the values for light properties of light sources or of illuminated surfaces will be discussed.

Explanations of luminous flux, luminous intensity and illuminance
In light measurements, the brightness is specified either for the light source or for the illuminated surfaces. In relation to the light source, a distinction can be made between the total emitted luminous flux in lumens and the luminous intensity in candela, which also takes the beam angle into account. One candela corresponds to one lumen per steradian, i.e. per solid angle unit. In the luminaires and lamps currently available, the luminous flux is almost always specified in lumens. To determine the luminous intensity in candela, the number of lumens must be divided by 4 π for a light source radiating uniformly in all directions, and by 2 π for a light source radiating only in a hemispherical way.

The term candela refers to candlelight. Thus, it is easy to remember that a candle flame shines with a luminous intensity of one candela. In contrast, a bright firefly has a luminous intensity of only 0.004 candela, and the daytime running lights on motor vehicles have a luminous intensity of at least 400 candela. The high beam of all headlights on a road vehicle may not shine brighter than 225,000 candela, and beacons used as orientation aids for seafaring may emit 35,000,000 candela, for example. The luminous flux and luminous intensity of luminaires and lighting elements are generally determined in the course of product development and during quality control at the manufacturers' with a special light measuring device.

While luminous flux and luminous intensity can be used to compare the light output of different light sources, illuminance describes how much light is incident on an illuminated surface. Illuminance is specified as an area-related quantity in lux, where one lux is defined as one lumen per square meter. Apart from the sun as a very strong light source, it is easy to see, even without a light meter, that the brightness of the light hitting a surface decreases with increasing distance from the light source. However, it is not only the distance from the light source that affects how much light arrives, but also additional light sources, shading, attenuation, and reflections from surrounding surfaces. The luminous intensity of elements for artificial lighting can also be weakened by aging or soiling. It is therefore advisable to check the illuminance at the relevant points on site not only immediately after installation, but also at regular intervals later with the help of the suitable light meter. In the case of technical systems for the use of sunlight, it is recommended to use the light meter before the installation to check which arrangement is the most favourable. After the installation, it can be checked whether the system achieves the promised performance for the amount of the incident light.

Selection criteria for the light meter to measure illuminance
First, the light meter must be suitable for the purpose of the measurement. This is not only a question of whether the luminous flux, luminous intensity or illuminance is to be determined. It is also important whether the light is to be used primarily for people, for plants or for technical purposes. Most light measurements are intended to measure the illuminance achieved for the particular light use at specific locations. Even if in each case the illuminance is measured in lux, the measured values of different devices at the same position and with the same illumination can differ considerably.

In order for the light meter to provide the appropriate values for the application, attention must be paid to the following:

Should the illuminance be measured according to human visual perception or for other purposes?
In the standard DIN EN 13032 Part 1, Annex B describes many device-specific parameters that have an influence on the measurement result of the light meter. For the measurements of illuminance in the workplaces, in recreation rooms, playgrounds, sports facilities and traffic routes, it is important that the measurement is made according to the spectral sensitivity of the human eye. The light meter should be able to detect and evaluate the visible spectrum of different light sources according to this spectral sensitivity. In addition, it must also be possible to detect obliquely incident light. For other purposes, the sensitivity to ultraviolet and infrared light, the evaluation of polarized light and of time-varying light, among others, can play a major role.

Should the light meter also be used to determine the color temperature of the light?
The light meter with additional equipment can also be used to measure light colors. The distribution of the wavelengths or frequencies of the radiation is characteristic for the perceived light color. The color of light not only affects the perception of the illuminated surfaces, it also influences many cell activities in living organisms. The color coordinates of light can be specified as primary colors in three-part additive color models, for example, as red, green, and blue values according to the CIE-RGB color space or as X, Y, and Z values according to the CIE-XYZ color space. Many models that measure the light color not only give the numerical values for the primary colors, but also show the color distribution of the measured light graphically on the colored device display.

Should the light meter be used continuously at the same position or at different measuring points?
Depending on whether the light meter is used for continuous monitoring of lighting conditions at a specific location or for the measurements at different locations, the requirements differ. In the case of the light meter that is to be used stationary in a light-sensitive production process, it makes sense to forward the measured values directly via interfaces to other devices for data evaluation or for controlling the lighting or shading equipment. In the case of devices that are used on as mobile devices at many different measuring points, attention should be paid to the storage options for the measured values. For certain measuring conditions, it is also advantageous if the light meter has an external sensor. The device can then be read-out and operated more easily without the risk of shading the sensor.

What measuring range and accuracy should the light meter have?
The measuring range is determined by the application. For many light measurements in recreation rooms, a measuring range of up to 2,000 lux or even 10,000 lux is sufficient. For work areas where a lot of light is required and when outside high illuminance levels from daylight must also be measured correctly, the measuring range should extend at least to 100,000 lux or beyond.

Based on its accuracy, the light meter can be classified in one of the accuracy classes according to DIN 5032 Part 7. These accuracy classes simplify the selection of device models. An instrument with the accuracy class C should only be used for orienting measurements. Class B and A instrument models can be used for measurements of lighting in businesses and public areas. For particularly precise measurements, on the other hand, the light meter of the highest accuracy class L should be used.

Can the light meter be calibrated and adjusted if necessary?
In the areas where too high or too low light intensity has a serious effect, it should be ensured that the measuring device used for testing works correctly. This is done by testing the accuracy of the measurements under specified conditions. Some instrument models can also be adjusted by the user. This means that these models can be readjusted if necessary to output the measurement results as accurately as possible .

Lighting and illumination have become essential in any sphere of life and they perform an auxiliary function when daylight is not enough or is absent. How much light is necessary? Is artificial light necessary if a natural light, both, inside and outside, is available? When is artificial light a huge help and when is it a complete waste?

A light meter is a device that helps to answer all these and other questions. It is a device which finds its application literally everywhere, from household to work places, streets, recreational and other facilities, illumination of the highspeed and other roads, all possible types of establishments and institutions. A very sensitive electrical device helps to monitor and control the level of illumination of any area. Lux is a standard, well-known unit, in which the measurements are expressed. Another possible term used in some systems may be foot candle (lumens per square foot).

Light meter is small in size, convenient to operate and since modern devices are equipped with a lighted screen (made of special glass), the reading of the measurements is significantly facilitated. Robust housing of the device protects the photocells from possible damages and excessive exposure to direct light of different origin (it may be natural sunlight, fluorescent light, high-intensity discharge lights, based on different gases).

The majority of people spend a big part of their day at work and it is natural that certain conditions should be created, so that the health and well-being of the workers was not damaged while they are performing their professional tasks. The quality of work and performance directly depends on how comfortable and safe the worker feels at the work place. Depending on the occupation, the amount of required light may differ tremendously. So, excessive light is as bad as scarce and this is quite a challenging task to create perfect working conditions for each particular task.

Besides, “comfort level” factor, which matters in general for any person, there is also “performance” factor. They now always coincide, due to a huge variety of jobs and tasks, but they should be kept in a certain balance. Educational establishments, hospitals, laboratories, factories etc. – these are the places where the level of light should be sufficient for 100% productivity. For example, if the light required is too bright or it should be too dim, the working process should be organized in such a way, so that the worker had enough breaks, allowing the eyes to relax, and was wearing respective eye protection. At the same time, it should not cause problems for the workers fulfilling other tasks, and whose comfort is totally disturbed by the improper lighting.

Arranging proper illumination for the workers performing their tasks outside is even more complicated, since it is difficult to predict and count on permanent stable illumination by natural light sources. That is why auxiliary lighting sources must be provided if the level of the natural light is not sufficient. The same relates to the professionals working in the dark time of the day or having late shifts. The range of workplaces and illumination requirements to them is extremely wide, but all of them have been classified and organized by the official authorities. Health care organizations pay a big attention to this issue, and numerous rules, standards and regulations are continuously discussed and monitored. The requirements to lighting at workplace may be found in the guidelines of International commission on Illumination, ISO 8995, Society of Light and Lighting (SLL) in Britain, European Norms, Illuminating Engineering Society of North America (IES) and similar organizations.

Humanity has developed a variety of man-made light sources to illuminate the dark and to light indoor spaces. Recommendations for indoor lighting depend on consumer preference and the location of the light source (e.g., home, office, school, parking lot, street, theater or hospital examination room, operating room, recovery room, etc.).

One of the most popular achievements in modern lighting technology is the light emitting diode (LED). LED lights can be found almost anywhere, inside and outside, and are available in different sizes and colors. The LED's greatest advantages are low energy consumption and long service life. These attributes make LEDs very attractive to consumers. LEDs do not emit as much heat as incandescent lights. Even when an LED light is on, there is no risk of burning the skin if the light bulb is touched. In addition, thanks to their epoxy lenses, LEDs are not too fragile. Though LEDs are quite popular nowadays, other types of indoor lighting still are widely used.

The aforementioned incandescent light has been used for decades in numerous indoor lighting applications. Incandescent light bulbs produce a soft and pleasant glow. This is why incandescent lighting still can be found in residential homes, even though incandescent light bulbs consume much more energy. Incandescent lamps get warm over time, and though the extra heat can help keep indoor temperatures warmer during the winter months, careful handling of recently or currently illuminated bulbs is required, because touching the hot light bulbs can burn the skin.

Another alternative to incandescent lighting is halogen lighting. Sometimes halogen light bulbs are selected for use in table lamps, inside and under cabinets, and in different wall-mounted fixtures. Halogen lights are small in size, contain halogen and inert gas, and offer a higher level of brightness and a longer service life.

Integrated compact fluorescent light (CFL) bulbs are reminiscent of incandescent light bulbs, because both kinds of bulbs feature the same base. Integrated CFLs can be used in many standard incandescent light fixtures. The difference between integrated CFL and incandescent light bulbs is that the service life is much longer (in average 8 – 13 hours) and the energy consumption is ¾ lower for integrated CFL bulbs. Aesthetically, the twisted-tube design of the integrated CFL bulbs looks much different than the egg-shaped design of the incandescent light bulbs. For this reason, some consumers prefer to use incandescent light bulbs in clear glass light fixtures.

Traditionally, when one thinks of fluorescent lighting, one envisions the long tube-shaped bulbs frequently used in industrial-looking overhead light fixtures. Since these large fluorescent bulbs produce a very bright light, they are often referred to as daylight lamps. Because there is a certain amount of mercury in these kinds of light bulbs, the bulbs should be handled and disposed of carefully.

Lastly, neon lighting can be found in some indoor environments. Neon lighting is comprised of electrified glass tubes filled with rarefied neon or other gases. The type of gas used in the tube determines the color of the neon light. Neon lights can be used for decorative lighting in bars and nightclubs as well as for small indicator lights in electronic displays.

Therefore, indoor light bulb selection largely depends upon the intended application. However, whether a light bulb is needed for ambient lighting, spotlighting or task-specific use, factors such as service life, energy consumption, aesthetics and price are almost always considered. In addition, special functions like dimming often are added to the equation. Only after analyzing all the required (and desired) lighting parameters can the best (most suitable) indoor lighting solution be identified.

A standard light meter is a useful tool for evaluating indoor lighting conditions, especially those involving incandescent and fluorescent light bulbs. When evaluating LED lighting indoors, an LED-specific light meter is recommended.

Warning lights are almost always coloured, as additional information can be provided via the colour. Warning lights in plants and on vehicles must be perceived even in bright daylight and concentrated activity or heavy traffic. They must therefore shine with high luminous intensity. As a general rule, warning lights in industrial areas should generally be five times brighter than the ambient lighting. For the warning lights on road vehicles, on the other hand, the light should be ten times brighter than that of the surrounding area.

The effective and peak luminous intensity of the warning lights can be measured with a lux meter and expressed in candela. The unit candela indicates the luminous flux in relation to the solid angle. The ECE-R65 test guidelines describe two different types of the warning lights that can be approved on the road vehicles. Class 1 includes beacons with a light level independent of the ambient light. Beacons where the light level is lowered at night belong to class 2.

Permanently installed or temporarily set up warning lights at construction sites, bridges, scaffolding or other danger points are intended to draw attention to the special situation, especially at night and in poor lighting conditions. To fulfil this purpose, it is important that the warning light shines brightly enough in the directions from which vehicles or pedestrians may approach. This can be checked with the lux meter for the respectively relevant distances.

Warning lights on cranes, masts, overhead power lines, towers, chimneys and buildings are also needed, especially at night. They have to be adjusted to the hazard to be expected in their position and height. For example, pilots should be able to detect potential collision points in the vicinity of airfields or hospitals with helipads in good time, even at night or in fog.

The purpose of emergency lighting is to ensure that in the event of power failures due to inadequate lighting, there will be no damage caused by faulty operation or accidents. According to the purpose of the emergency lighting, it can be divided into backup lighting and safety lighting. Backup lighting is used almost only in critical areas where normal lighting cannot continue to operate for a sufficiently long time using an emergency power supply.

The backup lighting is intended to guarantee, independently of the normal lighting, that the necessary activities can continue under suitable lighting conditions. For this reason, the illuminance of the backup lighting is usually selected to be as high as that of the normal lighting. This illuminance should be checked at regular intervals with the lux meter for both general and backup lighting.

The safety lighting is often planned and executed with lower illuminance levels than the normal lighting. It is intended to enable orientation in and safe exit out of the building in the event of failure of the normal lighting. In addition to illuminating escape and rescue routes, danger points, signs and warning devices, the safety lighting is also used to prevent panic situations.

The illuminance for the safety lighting must be selected according to the user group and local conditions. Separate regulations for safety lighting exist, for example, for meeting places, sports facilities, catering establishments, accommodation facilities, sales outlets, schools, hospitals, nursing homes, high-rise buildings and large garages. During regular inspections of safety lighting, the illuminance must be tested under suitable ambient conditions with the suitable lux meter.

EN 50172 Safety lighting systems
The European standard EN 50172 specifies the minimum requirements for the design, monitoring and maintenance of electrical safety lighting systems in workplaces and in structures where people congregate. It also points out national specifics.

DIN EN 1838 Applied lighting technology – Emergency lighting
The national editions of EN 1838 specifically regulate where safety lighting and safety signs must be installed and how they must be checked. Annex A describes the specifications for measuring luminance and illumination and for the lux meters to be used, and Annex B lists the national deviations.

For first-aid stations as well as fire alarm and firefighting equipment, the illuminance of at least five lux must be achieved via the safety lighting. Escape routes in Germany must have an illuminance of at least one lux along the centre line in an emergency, and the centre area of the escape route must have at least 0.5 lux.

Since large differences in brightness between lighting and background can lead to glare or missing dimly lit signs and obstacles, the following luminous intensities should not be exceeded in accordance with EN 1838:

For tests of the safety lighting according to EN 1838, the lux meters must meet the following requirements:

• To measure the luminance of safety signs, the light meter must have a V(λ) correction.
• To determine the illuminance, the measurements must be made with a cosine and V(λ)-corrected lux meter.
• The error limit of the measuring devices must not exceed ten percent.

Workplaces where inadequate lighting poses hazards to workers, the surrounding area or the general public should be equipped with emergency lighting to minimize these hazards. In general, the required emergency lighting should ensure that, in the event of a failure of the normal lighting, the brightness in the affected area is sufficient to identify escape routes, warning, auxiliary and signalling devices and to carry out safety-relevant activities. The specific requirements for planning, installing and testing emergency lighting are defined in directives and standards. There are some country-specific features.

The Directives issued by the Council of the European Communities apply to all member states of the European Communities.

Directive 89/654/EEC, which defines the minimum safety and health requirements for workplaces, also specifies the requirements for emergency lighting.

• "Escape routes and emergency exits where lighting is required must be provided with
  adequate emergency lighting for the event if the lighting fails"
• "Workplaces in which the workers are particularly exposed to hazards in the event of the
  failure of the artificial lighting, must have adequate safety lighting."

Important European standards issued on the subject of emergency lighting include:

The minimum illuminance values specified in EN 1838 are not minimum values for the design purposes, but for the maintenance values that must be achieved throughout the service life. Compliance with these values can be checked during regular inspections by taking measurements with a lux meter. Irrespective of these minimum values, the lux meter can be used to prove that the required uniformity of the illumination is maintained with a ratio of the lowest to the highest value of 1 : 40 for escape routes and 1 : 10 for workplaces with special hazards. The colour rendering index of the safety lighting, which should be at least 40, can also be measured with the suitable lux meter.

EN 1838 states that the proof can be provided by measurements or binding information from the manufacturer. Since deviations and defects of individual luminaires or lamps, their aging, possible soiling and special local conditions have an influence on the illuminance, on-site measurements with the lux meter should be preferred.

Germany
In the Point 7 of the Technical Regulation for Workplaces ASR A3.4 it goes about the safety lighting for activities, workplaces, work rooms and areas. It states that illuminance needs to be adapted to the hazard situation on site.

• Along the escape routes, the illuminance must be measured twenty centimetres above the floor or stair tread with the suitable lux meter.
• In work areas with safety lighting, the illuminance must be at least fifteen lux unless a higher value has been specified in the risk assessment. The measurements should be made with the lux meter at the position of the visual task.

France
In France, only specially certified emergency luminaires may be used. For anti-panic lighting, these emergency luminaires must emit at least five lumens per square meter. Regardless of this, at least two luminaires are required per room. The distance between several emergency luminaires must not be greater than four times their distance from the ground, and not greater than fifteen meters on escape routes.

Italy
For venues such as cinemas or theatres, Italy requires an illuminance of at least five lux in the area of stairways and exits and at least two lux along the rest of the escape routes. The values must be measurable on site. They must be checked with the lux meter at a height of one meter above the floor.

Great Britain
In Great Britain, the requirements for emergency lighting are regulated in British Standard BS 5266. One of the requirements is that emergency lighting should take effect 5 seconds after the failure of the general lighting system. An extension of this period to 15 seconds is possible in the buildings used mainly by people who know the escape routes.

The United States Occupational Safety and Health Administration (OSHA) requires adequate marking and lighting for each escape route. OSHA's standards, which serve as a basis for assessment, specify the required brightness for signs in escape routes both in the American units such as foot-candles or footlamberts and in the SI units such as lux or candela per square meter. Checks of the required brightness can therefore be performed both with the lux meter designed for American units and with the lux meter that displays SI units.

In the current Life Safety Code 101 of the National Fire Protection Association, the Section 7.9 deals with the regulations for the emergency lighting design. The brightness should achieve the average one foot-candle (10.76 lux) and not less than 0.1 foot-candle (1.08 lux) at any point along the escape routes for ninety minutes after the failure of the regular lighting. No SI units are listed in this American standard. If the lux meter is used that cannot display a foot-candle, the lux values obtained must be converted.

1 lux = 0.0929 foot-candle

Emergency lighting for workplaces in Australia
In Australia, the National Construction Code (NCC) regulates which buildings and areas require emergency lighting. Any building accessible to the public or to employees or customers must be equipped with emergency lighting. The Australian Standard AS/NZS 2293 contains the regulations for the design, installation, operation of emergency lighting and escape route marking. It requires a minimum brightness of one lux for emergency lighting on stairs, an average of at least 0.5 lux on floors, and 0.2 lux as a minimum value. Part two of the standard describes the checks and maintenance that must be carried out and documented every six months, twelve months and every 10 years respectively.

In the workplace, the illuminance should be adapted to the visual tasks of the activity. Good lighting is one of the prerequisites for safe and error-free work. Depending on the work task, the minimum illuminance values can vary greatly. For processing or visual inspection of very small details, illuminance levels of 1,000, 1,500 or even 2,000 lux are required. In contrast, in storage areas where only similar large parts are moved but not inspected, it is sufficient to determine an average illuminance of at least 50 lux with the light meter.

Too low brightness requires high concentration and leads to higher time requirements and faster fatigue. Excessive differences in brightness in the field of vision and glare caused by excessively bright light or reflections are also disturbing. When planning lighting, it is not only necessary to ensure that the work areas are sufficiently and as uniformly illuminated as possible. In the lighting design it must be also considered what the brightness and the gloss level of the walls and ceilings surrounding the workstation are.

When checking the actual lighting situation in the workplaces, a grid of several measuring points in the lighting level must be measured with the light meter. The values determined must be documented. On the one hand, it must be demonstrated that the average illuminance on the work surfaces corresponds at least to the specifications for the activity. On the other hand, the illuminance of the surrounding area must be determined by additional measurements in the vicinity of the work surfaces. The light meters used for the orienting measurements should correspond in their accuracy at least to class C according to DIN 5035 part 6.

In almost all work areas, LED luminaires have now proven to be an energy-saving alternative to other light sources. Due to the EU Ecodesign Directive with Regulation (EU) 2019/2020, after incandescent lamps, many fluorescent and halogen lamps with comparatively high energy consumption will also be removed from the market. Nevertheless, there are still a large number of light sources with different light spectra. High-quality light meters enable a correction of the measured value adapted to the spectral bandwidth and distribution of the respective light source.

The main contents of the BG 131 "Natural and artificial lighting of workplaces" were incorporated into the ASR A3.4 "Lighting" technical guideline for workplaces in 2011. As with other requirements relating to safety and health protection, the PAs also provide targeted support to their member companies in implementing the specifications for lighting.

Since the 2011 edition, ASR A3.4 has been consistent in many areas with the European standard EN 12464. This has significantly simplified the simultaneous application of both standards. In individual cases, however, there are deviations in order to achieve a higher level of protection for workplaces. Depending on the type of activity and ambient conditions, other standards must be considered when planning and maintaining the workplace lighting.

Here is a non-exhaustive list of important regulations for workplace lighting:

• Workplace ordinance (ArbStättV),
• Technical regulation for workplaces ASR A3.4 "Lighting"
• DIN EN 12464-1 "Light and lighting – Lighting of workplaces, Part 1: Indoor workplaces"
• DIN EN 12464-2 "Light and lighting – Lighting of workplaces, Part 2: Outdoor workplaces",
• DIN EN ISO 9241-6 "Ergonomic requirements for office activities with visual display terminals, Part 6 Guiding principles for the working environment"
• DIN 5032-7 "Light measurement, part 7 Classification of illuminance and luminance measuring instruments"
• DIN 5034-1 "Daylight in indoor areas, Part 1 General requirements"
• DIN 5035-6 "Lighting with artificial light, Part 6 Measurement and evaluation"
• DIN 5035-8 "Lighting with artificial light, Part 8 Workplace luminaires, requirements, recommendations and testing"

The German Social Accident Insurance, with the support of the employers' liability insurance associations, has published a range of information explaining how to implement the requirements for the workplace lighting:

• DGUV Information 215-210 "Natural and artificial lighting of workplaces",
• DGUV Information 215-211 "Daylight in the workplace",
• DGUV Information 215-220 "Non-visual effects of light on humans",
• DGUV Information 215-411 "Display screen and office workplaces",
• DGUV Information 215-442 "Lighting in offices – Aids for planning lighting systems for rooms with VDU and office workplaces".
• DGUV Information 215-444 "Sun protection in the office",
• DGUV Principle 315-201 "Requirements for the training of competent persons for the inspection and assessment of lighting in the workplaces".

Orienting measurements with a lux meter
Orienting measurements of the lighting at the workplace allow an assessment of the actual situation, considering the ambient conditions. The checks can be carried out by competent employees of the company using a suitable lux meter. Prior to the measurement, a measurement grid must be defined which is to be used not only for this series of measurements but also for subsequent regular maintenance.

ASR A3.4 states with regard to the lux meter:
"If the orienting measurements are carried out during the operation with the purpose of selecting or testing lighting equipment, illuminance meters that comply with at least Class C in accordance with DIN 5035 Part 6, 2006-11 edition, are to be used."

The measurement results are to be evaluated with regard to compliance with the minimum values as well as the achievement of the required uniformity. In the workplaces where the activity requires a high colour rendering index, this should also be checked. Some lux meters allow not only illuminance to be measured but also the colour rendering index. If there is any doubt about the usability of the measurement results, the experts should be consulted. They can carry out specific measurements in accordance with DIN 5035-6 "Lighting with artificial light, Part 6 - Measurement and evaluation" and, in connection with this, provide advice on how to carry out subsequent orienting measurements.

In Great Britain, too, mandatory requirements for the workplace lighting are specified in many official regulations.

• "Health and Safety at Work etc. Act 1974" in short also HSW, HSWA, HASAW 1974 or HASAWA,
• "Management of Health and Safety at Work Regulations 1999",
• "The Workplace (Health, Safety and Welfare) Regulations 1992",
• "Health and Safety (Display Screen Equipment) Regulations 1992",
• "Provision and Use of Work Equipment Regulations 1998",
• "Electricity at Work Regulations 1989",
• "Control of Substances Hazardous to Health Regulations 1999 (COSHH)",
• "Health and Safety (Consultation with Employees) Regulations 2002."

Other legal regulations determine the industry-specific workplace lighting requirements.

BS ISO 8995 "Lighting of indoor work places" is the British equivalent of ISO 8995/CIE S 008/E and implements its contents into national law. This standard defines the parameters of illuminance, glare and colour rendering for indoor workplaces for variously demanding activities. To ensure good lighting, not only the quantity of light but also its spatial and spectral distribution must be considered. The standard provides the basis for assessing the lighting of workplaces in offices, agricultural buildings, many different craft or industrial buildings, but also for schools, churches, libraries.

The British Standard BS 667 "Illuminance meters. Requirements and test methods" specifies the requirements for lux meters and test methods. It defines two classes of light meters, Class F for field measurements and the more accurate Class L for laboratory measurements. The requirements for the type L lux meter according to this standard are the same as those required for lux the meters by the British-European BS EN 13032-1. However, BS EN 13032-1 requires additional characteristics.

In the USA, the lighting requirements for the workplaces are also divided into general lighting, task-related lighting, and emergency lighting in the event that the general power supply fails. According to the standard 1926.56 of the occupational Safety and Health Administration (OSHA), the following minimum values for the general lighting apply to the workplaces where at least one employee is present:

- for concrete work, excavations, for refuelling, waste storage areas, loading docks, storage areas, maintenance aisles
          3-foot candles,

- in tunnels and shafts
           5-foot candles,

- in indoor areas of construction sites and warehouses, in hallways, corridors and along escape routes
           5-foot candles,

- in factories, sales areas, showrooms, storage areas, indoor washrooms
           10-foot candles,

- in offices, first aid stations and hospitals
           30-foot candles.

For work areas not covered by those described, the recommendations of the American Standard A11.1-1965, R1970 are the basis for the evaluation.

All values in the OSHA standard are specified in the foot-candle unit of measurement commonly used in America. An illuminance of one foot-candle is equivalent to one lumen over an area of one square foot. The SI unit lux, on the other hand, represents one lumen per square meter of the illuminated area. Many lux meters can display readings in both foot-candle and lux. If the lux meter does not provide the desired unit, the values can be easily converted. The conversion factor between foot-candles and lux is thus equivalent to that between square meters and square feet.

In Australia, the minimum illuminance requirements for occupational health and safety have been specified in Australian Standard AS(/NZS) 1680 "Interior and workplace lighting". Part 3 of this series of standards deals with the measurement, calculation and evaluation of the lighting data, and Part 4 with the maintenance of the electrical lighting.

The aim of enforcing the requirements is to ensure that

- each employee can perform his tasks without safety and health risks,
- every employee can move around the workplace without safety and health risks, and
- every employee can leave his workplace safely in dangerous situations.

The lighting situation in the workplaces must be checked on site with a suitable lux meter in accordance with the cycles specified in the planning. The lux meter used must have sufficient accuracy for all light sources to be tested in operation. If the measured values do not correspond to the specifications, the lighting must be adjusted.