TITLE:

ES&H Manual

 

DOCUMENT ID:

6105 Appendix T1

Guidelines for Office Ergonomics

 

 

1.0            Introduction

 

Ergonomics is the matching of the work environment, tools, and the people who use them.  Good ergonomics promotes productivity, minimizes physical distractions, and reduces the risk of injury and illness.  Unlike many occupational safety and health issues, ergonomic considerations vary highly with the person, his or her physical characteristics and preferred working style.

 

It is important to understand that the body’s response to cumulative trauma makes no distinction between on-the-job, at-home, or recreational activities.  Prolonged, repetitive motion – especially when it is forceful and requires unnatural joint deflection – will likely cause strain injury.  Similarly, prolonged sitting in an incorrectly sized or adjusted chair or one with poor support is likely to cause leg, back, and upper torso pain.  A computer screen with glare and poor image resolution causes eyestrain and corrective lenses need to be compatible with all of our activities – including home and office computer use.

 

2.0            Computer & Workstation Equipment

 

The computer’s role as an essential office (and home) resource has developed faster than has general public understanding of potential problems from poor body alignment and effects from long hours in front of a keyboard and screen.  Moreover, since these conditions typically do not cause acute pain or other immediate warning signs, many people are slow to connect their initial discomfort to their computer use and associated poor ergonomics.  A stiff neck or low-grade headache at the end of the day caused by hours in front of a poorly located computer monitor feels like any other bout of headache or stiff neck.

 

Variety in motion is an important strategy in preventing all repetitive strain injuries, including those associated with computer use.  Break up long sessions of keyboarding with other tasks.  Take stretch breaks regularly; get up and walk around even if you have no particular need to do so.

 

This appendix discusses some universally applicable recommendations that will be helpful to you – at work and at home.  Use them to choose and use your computer and related equipment to align your physiology with your tasks.  If you are a supervisor making purchase choices about a staff member’s workstation, be alert to the penalty exacted by poor ergonomics.  Even a small impairment to productivity because of eyestrain or physical misalignment will cost more than the proper equipment.  An ergonomics-related injury will likely cost many times over what the proper equipment would.

 

Consult with your Environmental, Safety, Health, and Quality (ESH&Q) staff and/or Occupational Medicine about ergonomic problems and solutions.

 

3.0            Chairs

 

The single most important piece of office workstation equipment is your chair.  Various studies have shown that 25 to 50 percent of workers who habitually sit in incorrectly fitted or mis-adjusted chairs suffer from back problems.  A poorly designed, improperly selected, or worn-out chair will defy all of your attempts to achieve proper posture. 

 

Height

If you need to purchase a chair, and you are not the “average 5’7” person,” an actual measurement is important to determine proper seat height.  Find a chair that allows you to sit with both feet flat on the floor and with thighs and shins exactly perpendicular.  Measure the distance from the hollow of your knees to the floor and subtract two inches.  This is the correct height for the chair seat from the floor.  Your new chair should have a range of height adjustments on either side of this measurement.

 

If the chair height is less than this optimum, the knees will be elevated, preventing the thighs from supporting the proper amount of torso weight.  This places stress on the buttocks and lower back.  (Note than an average adult has over 100 pounds of torso weight; the greater the load-bearing surface, the better.)

 

If, on the other hand, the chair is too high, excessive pressure is placed on the thighs at the front edge of the seat, possibly causing loss of circulation to the lower legs.  Chairs with worn-out cushions can cause this also, even at the correct height.  A downward-turned front edge on the seat is a good design feature, reducing pressure on your thigh.

 

The depth of the seat is important too.  If you are taller than average, select a chair that supports your thighs to within 2-3 inches of your inner knee surface.  If you’re shorter than average, avoid a chair seat that pushes into the back of your knee or that prevents your lower leg from extending straight down.

 

Adjustability

Most people will use whatever chair they are given.  If it is not adjustable or can only be adjusted with great difficulty, they will use it as found.  Loss of productivity is almost guaranteed due to back, leg, and foot discomfort.

 

If more than one person uses a computer workstation, the chair should be easily adjustable, with pneumatic-type adjustments.  Obviously, the range of adjustment should accommodate all of the chair users.  Any minimally suitable chair will have adjustments for seat and back height, armrest height, tilt tension, and back angle.  Better quality chairs will also have adjustments for lumbar-support-area height, armrest angle, seat tilt, and the distance from seat edge to chair back.

 

Chair Back

The lower curve of the back (the lumbar area) should be well supported by the chair back.  The chair should maintain the spine's normal, erect curvature.  Since people are proportioned differently, the chair-back elevation and/or the lumbar-support feature should also be adjustable.  Some chairs have the additional capability to allow the chair back to be adjusted horizontally relative to the seat.

 

Arm Rests

Armrests are somewhat misnamed.  They actually benefit the upper body by supporting the arms.  Though they are generally advantageous, many people who do lots of keyboarding do not care for arm rests.  Their objections often are related to experiences with full-length “executive chair” armrests that prevent chairs from being positioned close enough to the keyboard.  Your arm should be supported slightly while typing in the position described under “Keyboard Height.”

 

Proper armrests need not be very long horizontally, but their height should be adjustable if more than one person uses the chair.  Some chairs allow the armrests to be swiveled outward when they are not needed.  Some chairs have provisions to remove the armrests, and this may be appropriate to do if they’re not needed. 

 

Stability

Older office chairs usually were equipped with four legs and casters.  These are potentially unstable and may tip if you lean forward between two legs.  Newer chairs have at least five legs.  Avoid any chair that is designed so that the leading edge of the seat extends farther than the radius of the legs; they are inherently unstable and can tip suddenly.

 

Casters should be selected for the type of floor surface.  Wide carpet casters on a hard floor make for an “elusive chair” which may roll away from you as you sit.  Narrow hard-surface casters dig into carpet, making the chair hard to roll.  Chair mats are needed for carpeted floors to prevent carpet wear and to make chair movement easier while seated – preventing possible backache from the exertion required to move a chair that is directly on the carpet.

 

4.0            Keyboard

 

Height

A keyboard at correct height allows your upper and lower arms to be at a ninety-degree angle while typing.  A prolonged period of work with angles more than 15-percent either way from this optimum position can cause pain in the shoulders, back, neck, arms and wrist.  Note that positioning the keyboard in your lap may well provide optimum alignment, and there are keyboard trays made for this purpose.

 

Angulation

The keyboard should be sloped in a manner that places your wrist in a straight or “neutral” position, or with only a slight tilt up or down.  Keyboards trays or drawers should be selected to accommodate tilt in either direction from “neutral.Some users find it beneficial to alter the keyboard angle through the day. 

 

Position

The keyboard should be squarely to your front.  Even a slight misalignment causes torsional stress on the upper body that results in fatigue and pain in the neck, shoulders and back.

 

Wrist Support

The wrists should be supported while typing.  If the workstation is well designed, the keyboard support surface may offer proper wrist support.  Most keyboards, however, cannot be properly angled without a need for supplementary wrist support.  Ideally, the support should be soft and allows skin to “breathe.There are a number of stand-alone wrist support devices on the market.  Most keyboard tray systems include this feature.

 

Keyboard Use

Typing force has an effect on the overall strain to your wrists and hands.  Most people type with excessive force, and people with chronic wrist/hand strain injuries often type with the greatest force.  Use a light touch, and be conscious of the angle of your wrists as you type.  There are ergonomic keyboard designs that attempt to match the plane of the keys to a more natural wrist and hand alignment.  Because the keys are angled outward and more difficult to see, these keyboard designs are of greatest benefit to touch typists.

 

5.0            Video Display Terminal (VDT) or Monitors

 

Height

The top of the screen should be at or slightly below eye level, with your head in a normal, erect position.  This is a very important parameter.  If you are forced to look downwards or upwards for prolonged periods, neck, back, and shoulder strain are likely.  There are a number of platforms or stands available to alter height and provide storage space for the keyboard or other items.  There are also pivoting support brackets that hold the VDT off the work surface altogether.  Note that an incorrect VDT height is almost certain to contribute to other posture problems as you unconsciously compensates for your position.

 

Tilt

Ideally, the screen surface should be perfectly vertical or a slight downward tilt (~10°).  This offers the best compromise between glare prevention and elimination of optical distortion.  Upward tilt invites reflections from overhead lighting.  Extreme tilt in either direction can cause image distortion, and it requires the eyes to change focus as they scan up and down the screen.

 

Position

As with the keyboard, the screen should be directly in front of you.  Twisting or turning motions during typing contribute to neck, shoulder and back discomfort.  Materials that are being read during typing should also be directly to the front.  This usually necessitates the use of a document holder.  It should hold the document as close as possible to the screen and at the same distance from the eye as the screen image.

 

Distance

The screen surface (which is not necessarily the front edge of the VDT) should be within 18 to 24 inches of your face.  In reality, the size of the screen and the display’s character size influence this measurement, and large VDTs can be positioned farther away.  In any event, you should not position the screen to compensate for vision problems; wear corrective lenses if you need them, and position the screen at the proper distance.

 

Brightness, Contrast, and Color

Most VDTs and monitors have both brightness and contrast adjustment controls.  The screen should be sufficiently bright to overcome incidental glare from lighting and windows, but excessive brightness can cause blurred screen characters and eyestrain.  Experiment with different contrast settings for different software to make best use of the background formats you use most often.  Likewise, experiment with color settings – especially for page backgrounds.  Stark-white page backgrounds may not be the best choice for long-term viewing.  Try an off-white or parchment-color page background.  Certain color combinations are obviously distracting and will cause eyestrain: adjacent red and green, for example.  Good contrast and image resolution are important no matter what colors are used.

 

Image

All cathode-ray-tube devices – televisions, VDTs, etc. – eventually lose image quality.  This usually takes years of normal use, but in time the phosphor coating on the screen deteriorates, causing loss of character resolution and color purity.  Also, prolonged display of unchanged images may cause these to be “burned” into the screen, although current monitor design makes this less of a problem than it once was.  In any event, screen-saver features help prevent these problems.  A VDT or monitor with a deteriorated image should be replaced.

 

Proper screen refresh rate prevents flicker.  Select a rate at the upper end of the range recommended by the monitor manufacturer.

 

Screen Maintenance

Cleanliness of the screen is important.  Smudges, dust, scratches and so forth, can blur the image and can cause the eye to attempt to focus in two planes simultaneously, causing strain.  This is particularly noticeable if a glare filter is used over the front of the screen and it is blemished.  These should be virtually undetectable to the eye when in use.

 

Document Holders

Documents that are being read during typing should not be flat on the desk.  They should be in a near vertical position, in the same focal plane as the VDT screen.  Avoid any need to turn the head or change eye focus while typing.  There is a wide selection of devices to hold paper and/or books in proper position, and price is not a good predictor of their suitability.

 

Corrective Lenses and VDT Use

Many visual problems associated with the use of VDTs can be traced directly to poor eye care.  Uncorrected or improperly corrected vision problems are more likely to cause or exacerbate visual fatigue, which affects how well you can see.  Your comfort, concentration, and your productivity are all negatively affected.

 

The purpose of corrective lenses is to bring your vision back into an acceptable range.  The use of corrective lenses should have no effect on your ability to use a VDT so long as the lens prescription factors in your computer use.  Near-vision correction (reading glasses) typically is selected for a reading distance of 12 to 18 inches, while computer monitors are often 24 inches or more from the eyes.  Be sure to tell your eye-care professional how much time you spend in front of a computer, and the height and distance of the monitor from your eyes.

 

Lenses recommended for VDT use, in usual order of preference, include:

·         the monofocal: single-prescription eyewear selected specifically for your type of computer use

·         the full-width or flat-top bifocal: different corrections for near and distance vision Bifocals can be a problem for VDT use.  Conventional reading-type bifocals may not be appropriate.  If you must tilt your head back or into an uncomfortable position to see the screen, you need a different type of lens.

·         and the progressive lens: the “no-line” lens that corrects vision in a gradual manner from near to distance.  Progressive lenses may not provide a sufficiently large zone of correction for the field of view required for the width and height of your monitor and your document holder.  Having to move your head back and forth or up and down to get proper focus on the entire screen indicates a problem.

 

6.0            Foot Support

 

Most people who must sit for prolonged periods find it more comfortable to have their feet in a slightly upward tilted position.  This can be accomplished with a makeshift footrest, but there are commercial products that offer adjustable angle and heights.  Using some type of foot support helps many people cope with chronic lower back problems.

 

7.0            Desk/Workstation

 

Height

Your desk height should allow proper arm alignment for keyboard use.  Most conventional desks are made with work surfaces higher than this optimum keyboard height, and although they may be ideal for writing and other functions, they will put a keyboard much higher than it should be.  Computer workstations usually provide a lower surface for a keyboard.  There are retrofit, roll-out shelves or trays available for conventional desks that put the keyboard at the proper height.  And remember the option of using the keyboard in your lap.

 

Work Area

At a minimum, the available surface area should accommodate the computer enclosure, the VDT or monitor, the document holder and the keyboard – observing good position parameters.  Matte-finish or non-glare surface colors help reduce reflected glare and associated eyestrain.

 

Leg Room

Most people are comfortable if they have about 25 to 28 inches vertical distance from the underside of the work surface to the floor.  Very tall individuals will need more distance.  There should be sufficient space for some lateral leg movement, and the front-to-back space beneath the desk should allow for periodic stretching of legs.  Avoid storing materials beneath your desk; it can interfere with proper leg extension and alignment.

 

8.0            Office Environments

 

Noise

Noise is an unavoidable feature of most offices.  It does have a serious penalty, however.  Stress, loss of concentration, and reduced productivity are all associated with noise.  It is important to remember, too, that one person's music can be another's noise.

 

In general, every effort should be made to keep nuisance noise to a minimum: phone ringing volume, office machinery, door slamming, etc.  Impact and ink jet-type computer printers generate considerable noise.  Resilient padding underneath the printer and printer enclosures can help make them quieter.  Office partitions often can help isolate or attenuate noise.  Carpeting, drapery and upholstery all absorb considerable noise energy.

 

Traffic

Traffic (as in people) in the work area is a powerful distraction.  Visual barriers are often needed to screen people with high-concentration tasks from passersby.  Some workstations have integral partitions.  Arrangement of the office can reduce traffic in the vicinity of desks and workstations. 

 

Wall Finish & Coverings

Wall paint or covering is a very effective means of controlling VDT screen glare.  Basic white is a poor choice for an office where computers are in frequent use; light grays, tans, blues and greens are usually better choices.  Reflectivity can be specified in paint selection.  Textured wall coverings may be preferable to paint in some settings.

 

Lighting

Lighting can enhance or hinder office operations.  VDT screen glare is known to cause eyestrain, headaches, and loss of concentration and productivity.  Unfortunately, computers are often in environments where other tasks are performed and where high illumination levels are needed.

 

Unless the VDT is in its own room, it will likely be subject to excessive ambient light levels and glare.  Windows are especially troublesome.  Evaluate glare with the VDT turned off; a black screen offers the best test surface for glare potential.  Occasionally, a glare filter or hood will be needed on a VDT to reduce stray light and glare on the screen.

 

Lighting measurement is not always a straightforward process either.  The most up-to-date guidelines for light levels address a number of variables such as reflectivity of the work surface, task performed, and so on.  If you suspect a problem, ask your ESH&Q staff to evaluate the lighting in your work area.

 

Room lighting for computer-only operations can be much lower than for general offices: 20 to 50 foot-candles as opposed to 80 or more.  Be aware, however, that many people feel uncomfortable at first in environments with this lower level of illumination.

 

Task lighting is often the best solution.  Whole room or ambient light level is kept to a safe (for walking) minimum, while desk lamps illuminate individual work areas to the necessary levels.  This usually offers considerable energy savings as well.  New, modular office workstation systems carry this concept to an advanced degree with integrated lighting systems.

 

Additional considerations when evaluating office lighting:

 

Fluorescent Lighting

Usually, general-purpose fluorescent lighting is not the best choice for computer environments.  It is often installed with excessive illumination levels, and its light is highly diffused (omni-directional), which promotes screen glare.  This does not mean that all fluorescent lighting is unsuitable.  It will likely benefit from some “fine tuning,” however.

 

Tube Color

There are several choices of light hue in fluorescent tubes: cool white, warm white and full spectrum.  There is some evidence that full spectrum causes less glare and is more pleasing to the average eye.

 

Diffusers

The grid or lens in a fluorescent fixture has a great deal of influence on glare production.  Egg-crate-types, which direct light downward, are often more suitable than prismatic types which tend to diffuse light in all directions.  Parabolic diffusers—a special type of grid—are perhaps optimal for computer areas.  Although they are more expensive, they do the best job of minimizing lateral glare.

 

Windows

Nearly everyone wants a window near his or her desk.  Natural light diffusing through a window is a powerful glare source, however.  Try to locate the VDT to minimize glare.  Windows near VDTs should have opaque blinds, and screens should be turned away from the window.

 

Direction of Light

Glare is produced when light reflects from the screen.  Although its original source may have been overhead lights or a window, walls and other reflective surfaces can contribute to glare problems.

 

Another related problem occurs when there is an illumination source within your field of vision while you attempts to focus on the screen or document.  The pupils adjust their dilation for the eyes' total light field, and that may not be consistent with the illumination in the primary focus field: the screen and document.  Eyestrain and headaches are possible outcomes.  Light-blocking partitions or repositioning the VDT are potential solutions.

 

Temperature and Humidity

The ideal office temperature is in the range of 72 to 75 degrees, with a relative humidity of 40 to 60 percent.  Unfortunately, there are many possible reasons why these conditions cannot always be maintained.  There are also biological differences in individuals' comfort levels, and majority rule is sometimes the only resolution.

 

Humidity is more important than many people realize – both for comfort and health.  Excessive humidity, especially in warm weather, causes discomfort.  It also has undesirable effects on office paper.  Very low humidity, on the other hand, can cause irritation of mucous membranes, even to the extent of nosebleeds.  Low humidity also promotes static electricity that can damage electronic devices.

 

Ventilation

All offices need fresh air to prevent normal indoor pollutants from reaching objectionable concentrations and to replenish oxygen used in respiration.  Fresh air is usually introduced into larger buildings by mechanical means: fan and damper systems that blend outside air with heating or cooling supply air, and by exhaust fans which draw air out of the building – often with their intakes near sources of potential contamination.

 

Fan systems are designed for a certain number of occupants.  If changes occur to space use and occupancy, the original ventilation design may become inadequate.  It is important to coordinate space-use decisions with Facilities Management to prevent problems later with poor air quality.

Persistent or recurring odors may be an indication that an area is not getting sufficient fresh air.  Mold and mildew growth is also a warning sign, and it should be taken seriously.  Call Facilities Management, your ESH&Q staff, and/or Occupational Medicine if you suspect there is a problem with your ventilation.

 

Radiation

In recent years, there has been a great deal of speculation and publicity about possible human health effects from radiation emitted from computer VDTs.  Early cathode-ray tubes, including those used in televisions, could emit X-rays – a type of ionizing radiation.  For many years, however, product manufacturing safety standards have made this problem negligible.

 

All electrical equipment can produce electromagnetic fields: non-ionizing radiation.  Even though VDTs have internal shielding, there can be detectable electromagnetic fields close by.  The energy of these fields diminishes quickly with distance, however, so that an operator sitting at the typical distance from the VDT gets an extremely low exposure.  Research to date suggests there are few if any health effects associated with this type of radiation in doses experienced by computer users.

 

In short, radiation from computer equipment is not a problem unless the shielding or case has been damaged or removed.  Even in that instance, electrical shock is a much greater concern.  Never use a piece of electronic equipment that you suspect is damaged, and never attempt to repair equipment unless you are trained and equipped to do so safely.

 

 

 

ISSUING AUTHORITY

APPENDIX AUTHOR

APPROVAL DATE

EFFECTIVE DATE

EXPIRATION DATE

REV.

 

 

 

ESH&Q Division

Jennifer Williams

02/06/06

02/06/06

02/06/09

0

 

This document is controlled as an on line file.  It may be printed but the print copy is not a controlled document.  It is the user’s responsibility to ensure that the document is the same revision as the current on line file.  This copy was printed on 8/24/2009.