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Why is lighting important?






Whether in industrial or office settings, proper

lighting makes all work 
tasks easier. 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 can prevent workplace accidents by 
increasing the
visibility of moving machinery and other safety hazards.
Good 
quality
lighting also reduces the chance of accidents and
injuries from 

"momentary blindness" (momentary low field vision
due to eyes adjusting from

brighter to darker, or vice-versa,
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.






What are other OSH Answer documents about


lighting?






Please also see:












What are different sources of
light?






Daylight: How much daylight

reaches inside a building
depends  on the architecture of the
building
(does the building have windows;
how big;  how are they
oriented?), the  amount and direction of sunlight, cloud
cover,  local
terrain, and the
season. The cleanliness of the windows is
important
as  well. 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.






Electric Lighting:  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.  The following
are
common types of
bulbs.


























































































































Table
Light Bulbs*
TypeCommon ApplicationEfficiencyColour Rendering**
Incandescenthomespoorgood
Fluorescentofficesgoodfair to good
Mercuryfactories, officesfairfair to moderate
Low pressure sodiumroadwaygoodpoor
High pressure sodiumfactories, commercialgoodfair to good
Metal Halidefactories, commercialgoodgood





* Bulbs are often referred to as lamps in many

technical publications.






** Colour rendering is the effect of light on the

colour of objects. 







What are basic types of artificial

lighting?






There are three basic types of

lighting:









     





  • General.







  • Localized-general







  • Local (or task).





General lighting provides fairly uniform

lighting.  An example would be
ceiling fixtures that light up large

areas.






General Lighting





Localized-general lighting uses overhead fixtures

in addition to ceiling
fixtures to increase lighting levels for
particular
tasks.






Localized general lighting





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.






Local or task lighting






What are different types of light

fixtures?






The complete lighting unit (also called the light

fixture) controls and
distributes the light.  (Light fixtures are
often
referred to as "luminaires" in
technical
publications.)






Various types of light fixtures are designed to

distribute light in different
ways.  These fixtures are known

as:









     





  • Direct.







  • Direct-indirect.







  • Indirect.







  • Shielded (various

    types).





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 toward the work area. 
Direct
lighting tends to create
shadows.






Direct light fixtures





Direct-indirect light fixtures

distribute light equally
upward and downward.  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.






Direct-indirect light fixtures





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.






Indirect light fixtures





Shielded light fixtures use

diffusers, lenses and louvers to
cover bulbs from direct view;
therefore,
helping to prevent glare and distribute
light.









     





  • Diffusers are translucent or semi-transparent

    (see-through) 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.





Shielded light fixtures








     





  • 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.





Parabolic louvers Egg-crate louver






Can electric lighting affect what we "see" as

the colours of an object?






Yes.  The "colour" of an object actually

depends upon the colour composition
of the light itself as well as the

colours of the light that the object reflects
and
absorbs.






Natural sunlight is made up of all the colours of

the rainbow (spectrum): 
red, orange, yellow, green, blue, indigo
and
violet.   Most electric lights do
not "make" of all these
colours
even though the lights appear to be emitting
"white" or "normal"

light.  In fact, different lights give different colour
rendering

characteristics.  As a result, the true colour of an object can only

be
determined when viewed under sunlight or under lighting, such as full


spectrum lighting, that has the same spectral composition as

sunlight.






For most work situations, colour rendering is not

an issue.  However, full
spectrum lighting may be needed
wh



 



en colour judgement is important; for example,




 



in a fabric manufacturing or sewing

environment.



 



Types of light emitted by different fixtures











ACCESSORIES AND OPTIONS



http://www.ccohs.ca/oshanswers/ergonomics/lighting_general.html

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