Appropriately placing lighting and
selecting the right level of illumination can enhance
your ability to see monitor images. For example, if lighting
is excessive or causes glare on the monitor screen, you
may develop eyestrain or headaches, and may have to work
in awkward postures to view the screen. Ventilation and
humidity levels in office work environments may affect
user comfort and productivity.
- Arrange your office to minimize
glare from overhead lights,
desk lamps, and windows.
- Maintain appropriate air
- Avoid sitting directly under
air conditioning vents that
"dump" air right
on top of you.
- Bright lights shining on the display screen
"wash out" images, making it difficult
to clearly see your work. Straining to view
objects on the screen can lead to eye fatigue.
Blinds are on the windows and the monitor
is placed at an angle (perpendicular)
Bright light entering from a window
- Place rows of lights parallel to your line
of sight (Figure 1).
- Provide light diffusers so that desk tasks
(writing, reading papers) can be performed while
limiting direct brightness on the computer screen.
- Remove the middle bulbs of 4-bulb fluorescent
light fixtures to reduce the brightness of the
light to levels more compatible with computer
tasks if diffusers or alternative light sources
are not available. Note:
a standard florescent light fixture on a nine-foot
ceiling with four, 40-watt bulbs will produce
approximately 50 foot-candles of light at the
- Provide supplemental task/desk lighting to
adequately illuminate writing and reading tasks
while limiting brightness around monitors.
- Generally, for paper tasks and offices
with CRT displays, office lighting should
range between 20 to 50 foot-candles. If
LCD monitors are in use, higher levels of
light are usually needed for the same viewing
tasks (up to 73 foot-candles).
- Bright light sources behind the display screen
can create contrast problems, making it difficult
to clearly see your work (Figure 2).
- Use blinds or drapes on windows to eliminate
bright light. Blinds and furniture placement
should be adjusted to allow light into the room,
but not directly into your field of view (Figure
1). Note: vertical
blinds work best for East/West facing windows
and horizontal blinds for North/South facing
- Use indirect or shielded lighting where possible
and avoid intense or uneven lighting in your
field of vision. Ensure that lamps have glare
shields or shades to direct light away from
your line of sight.
- Reorient the workstation so bright lights
from open windows are at right angles with the
computer screen (Figure 1).
- High contrast between light and dark areas
of the computer screen, horizontal work surface,
and surrounding areas can cause eye fatigue
- For computer work, use well-distributed diffuse
light. The advantage of diffuse lighting is
- There are fewer hot spots (or glare surfaces)
in the visual field, and
- The contrasts created by the shape of objects
tend to be softer.
- Use light, matte colors and finishes on walls
and ceilings to better reflect indirect lighting
and reduce dark shadows and contrast.
Glare from overhead light source
Monitor with a glare screen
a large number of low powered
lamps rather than a small
number of high powered lamps
will result in less glare.
- Direct light sources (for example, windows,
overhead lights) that cause reflected light
to show up on the monitor (Figure 3) make images
more difficult to see, resulting in eye strain
- Place the face of the display screen at right
angles to windows and light sources. Position
task lighting (for example, a desk lamp) so
the light does not reflect on the screen (Figure
- Clean the monitor frequently. A layer of dust
can contribute to glare.
- Use blinds or drapes on windows to help reduce
glare (Figure 1). Note:
vertical blinds work best for East/West facing
windows and horizontal blinds for North/South
- Use glare filters that attach directly to
the surface of the monitor to reduce glare (Figure
4). Glare filters, when used, should not significantly
decrease screen visibility. Install louvers,
or "egg crates", in overhead lights
to re-direct lighting.
- Use barriers or light diffusers on fixtures
to reduce glare from overhead lighting.
- Reflected light from polished surfaces, such
as a keyboards, may cause annoyance, discomfort,
or loss in visual performance and visibility.
- To limit reflection from walls and work surfaces
around the screen, paint them with a medium
colored, non-reflective paint. Arrange workstations
and lighting to avoid reflected glare on the
display screen or surrounding surfaces.
- Tilt down the monitor slightly to prevent
it from reflecting overhead light.
- Set the computer monitor for dark characters
on a light background; they are less affected
by reflections than are light characters on
a dark background.
- Users may experience discomfort from poorly
designed or malfunctioning ventilation systems,
for example, air conditioners or heaters that
directly "dump" air on users.
- Dry air can dry the eyes (especially if the
user wears contact lenses).
- Poor air circulation can result in stuffy
or stagnant conditions.
- Temperatures above or below standard comfort
levels can affect comfort and productivity.
Air ventilation diffuser
- Do not place desks, chairs, and other office
furniture directly under air conditioning vents
unless the vents are designed to redirect the
air flow away from these areas.
- Use diffusers or blocks to redirect and mix
air flows from ventilation systems (Figure 6).
- Keep air flow rates within three and six
inches per second (7.5 and 15 centimeters
per second). These air flow rates are barely
noticeable or not noticeable at all.
- Keep relative humidity of the air between
30% and 60%.
- The recommended ambient indoor temperatures
range between 68° and 74° F (20°
and 23.5° C) during heating season and between
73° and 78° F (23° and 26° C)
during the cooling season.
- Exposure to chemicals, volatile organic compounds
(VOCs), ozone, and particles from computers
and their peripherals (for example, laser printers)
may cause discomfort or health problems.
- Enquire about the potential for a computer
or its components to emit pollutants. Those
that do should be placed in well-ventilated
- Maintain proper ventilation to ensure that
there is an adequate supply of fresh air.
- Allow new equipment to "air out"
in a well-ventilated area prior to installing.