.Augusto's Electrical Safety & Reliability . .

Created: 1999-06-22
Last edited: 2001-08-08

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Lighting Safety & Functionality Survey .

The information below is a brief resume, it could be useful to get some general technical culture about lighting that any civilized human needs in daily life, but basic education some times does not provide; the information is also a base to prepare a detailed survey on lighting systems, so it could be of interest to Architects, Electrical Engineers, Industry and Construction Engineers and Technicians, Maintenance people, General Managers.

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GENERAL INDEX.

Lighting, Safety & Efficiency.

Prod 990622 Rev. 0
Author : Augusto Mendoza-Martinez

Concepts.- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01

1. Lighting is a general use word ... be careful !, some different words and expressions with precise meanings are related to this use of energy that helps humans seeing under low or non existing, natural light conditions. If word's precise meaning is not taken into consideration, information cannot be received nor transmitted without misunderstandings that some times turn useful information into error and lost of time, money and property. To the safe use of this page by non trained people I will include some simple explanations about the meaning of certain words and basic concepts that can also be useful to increase general culture on this very important technical aspect.
   
   
2. Not always Safety [ * ] but Efficiency is more related to modern normal lighting. Human eye can automatically adapts, within a wide range of lighting conditions, to visually perceive in order to perform an activity. Lighting quantity and quality factors needed to perform activities efficiently [ time consume, low rate of error, not fatigue effects, etc.] have been investigated by Electrical Lighting Engineers, Scientists, Occupational Health Doctors and some others, to set recommended lighting conditions for different activities [visual tasks], age groups, etc. The most advanced technical and scientific information can be found in IES [Illuminating Engineering Society from North America].
   

   [ * ] Safety . . . isn’t the lack of danger, this is never true, and we all have to learn living with some risks. All what one can do is to control the appearance of dangerous situations, or to produce some automatic actions to reduce the time during the dangerous situation is present, or to have automatic means to reduce the time, magnitude or both of events. Therefore, safety in this context means only risk control ....
   

3. Visual Perception and Light Facts more related to lighting technology, and about what you are invited to think and get conclusions, are the following . . .
   

   [1] The eye in humans can detect a range of light wave frequencies [same as colors] and transform them into biological information ready to be processed by brain. The color of an object really means that the objects [roughly speaking] absorbs all light spectrum but the light color we see; this color is reflected in some important percentage.

   [2] Detection efficiency is different with different colors of light [yellow has the lowest detection threshold, so this color is best detected]. Natural [sun] light is a blend of light wavelenghts that changes along day cycle; this light so allow seeing all different colors human can see.

   [3] At low levels of light energy [at night] eye detectors system cannot distinguish colors but light or no light; that is darkness [black and white vision].

   [4] Detection is done from a field in front of pair of eyes in a like photographic device way. The two pictures are conbined by brain in a single 3-D vision of the covered field.

   [5] Human eyes receive light mainly from three zones: the OBJECT where you look at [the task], the BACKGROUND is composed by the immediate surroundings and the general surroundings.

   [6] The eye, to get enough light to see and to protect sensors [retina] from burns, must control light entrance, opening or closing the iris automatically; so the eye adapts continuously to the media of the light [luminance] that enters to the retina [sensors interior eye area]. Time to adapt to darkness is slow but adapting to higher lighting conditions is fast even sometimes it hurts.

   To maintain visual perception during the change from high light to low light, the rate of fading in time must be slow enough to let the eye to adapt.

   To no feel discomfort or pain and become dazzled losting visual perception, during the change from low light to high light, the rate of light increase in time must be slow enough to let the eye to adapt.

   Eye can see within a huge range of lighting [Outdoors on a sunny day 200,000.00 Lux and even more, to o.10 Lux or some less at night].

   [7] Because some automatic biological response eyes sight is directed to light; if your brain orders to see one object, eyes will scan background field to lock at the strongest light emitting or reflecting surface and also the object ordered by brain, alternatively.

   [8] Brain recognize using differences of light perceptions coming from the exterior thorough the eye system, with the help of previous learning: shapes, limits, objects, letters and signs of writing, etc. In other words you can perceive only if there is enough contrast [white traces on white paper cannot be seen, a hole in a road is perceived by the contrast between shaded walls of the hole against grey surface of the flat road].

   [9] 3D vision is possible because of the different information that receives the left eye from that of the right one, processed by the brain using stored data from the learning process [distances perception, volume perception]; this fact leads some to well known visual illusions.

   [10]The eye can capture Light from sources of that kind of energy [incandescent objects, fire, lamps, sun, etc.]; All kind of surfaces receiving light from some source [lighting system fixtures] absorb part of the energy and reflect the balance; reflected light can go to other surfaces to be reflected partially again and again; reflected light is also used by the eye system to get information. Light captured is used to feed the brain and see light sources or objects that can reflect light [a non-reflecting glass cannot be seen; a red object is difficult to see if lighted with blue or green pure light ].

   [11] Once retina receives light becomes exited and stay so during certain time after light energy stops hitting sensors [retina memory ]; this fact permits seeing TV and action without jumps at the movies, but also can lead to wrong dangerous perceptions like seeing stationary or moving at low speed a wheel rotating at high speed, if the lighting emission is periodically fluctuating [stroboscopic effect].

   [12] Because the eye system is aimed automatically to the object of higher luminance in the visual field, it becomes adapted mainly to the light received from that part of the visual field, so other objects sending less light to the eye system can be not seen or hardly seen. This is known as glare [direct or by reflection].

   [13] Working with a very different luminance background to that of the task can lead to eye fatigue because of continuous changing of iris opening; The regular change of lighting, between a range of changes by second [danger range of frequencies], if last for some time will produce loss of perception capacity and hypnosis.

   14] Moving people [ walking along a corridor, driving a vehicle on a road, piloting an aircraft on landing] in a changing of lighting conditions path, means the eye must adapt to perceive, if the speed not fast enough to allow the retina memory make the changes in lighting not perceivable. If changing rate of lighting as perceived by moving observer is faster than eye adaptation speed, observer will loss visual perception [ entering a parking building whose entrance has no good lighting relation to the exterior; driving towards an underpass o tunnel if such part of the traffic way is not properly lighted - you become blind during the time your eye has not become adapted; you perceive the underpass tunnel interior as a black hole].

   15] Artificial light sources [ flame, incandescent gas burners in camping lamps, metallic filaments made incandescent by electric current, electric discharge arches, electric discharge arches in gas and vapors blends, fluorescent exited substances, etc.] are used by lamp manufacturers to put in the market a wide range of practical solutions to select the best suited to each case or application [ physical size, emitting light, lumen per watt efficiency, light color, life, starting time, re-starting time, feasibility of dimming, working temperature, etc.]. ....
   

4. Emergency Lighting is the one related to safety. . . What could happen if you have to run out a place and because of an energy failure you find yourself in dark?... There are many cases when some lighting it is needed to replace the Normal Lighting when it fails, if this lighting is required to protect life or property it is named Emergency Lighting which includes: Exit Lighting, Safety Lighting, Security Lighting, Stand-by Lighting.
   
   [ * ] Exit Lighting. . . To identify, and use efficiently the Means of Egress and ways designed to go to a safe place in case of an emergency [fire, earthquake, war situation, terrorist action, etc] ....
   
   [ * ] Safety Lighting. . . To stay at working places or perform some duty safely during the Normal Lighting outage ....
   
   [ * ] Security Lighting. . . To protect people and property against crime ...
   
   [ * ] Security Lighting - Surveillance . . . To detect and see intruders.
   
   [ * ] Security Lighting - Protective . . . To deter potential intruders ...
   
   [ * ] Security Lighting - Safety . . . To grant safety or protection to circulation of security people ...
   
   [ * ] Stand-by Lighting. . . To maintain certain normal activities to continue during certain time or continuously ....
   
   
5. Emergency Lighting Functioning is either Normally On or Normally Off; First one when it is part of normal lighting, and in the event of normal energy source failure, becomes energized by an Emergency Energy Source and stay working or restart in an appropriate time. The second one, if emergency fixtures are off when normal light is working properly, but lit when normal light goes out. Because of cost, quantity and quality factors of lighting that standards require for Emergency Lighting are the real minimum acceptable, well below the standards recommendations to normal lighting.
   

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Importance of Lighting.- . . .. . . . . . . . . .. . . . . . . . . . . . .02

1. Not properly Lighted installations can produce, from low efficiency of business, lost of quality in products or services you sell, to very serious injures and even death to people .
   
   
2. Codes and Standards provide rules and technical support to the planners, constructors and maintenance people to do the right way . Unfortunately managing staff not always has the minimum knowledge to understand enough situations about lighting and actions do not follow the best approach the up to date knowledge can provide.

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I do recommend.- . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . 03

1. Review, or make others do, your lighting installation and equipment to be sure them are properly used.
   
   
2. Be wise to search qualified advice and action if you find any undesirable situation listed here is present in your case.
   

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You are also invited to read some about:

• Economics.
• Interesting Quotations.
• If History tells the truth ...then why ?.
• General Safety & Health.

Last Rev. 1. - 2001-08-08