Office Ergonomics Standard

The evolution of "Office Ergonomics" has been due largely to the rapid growth of information technology. Consequently, individuals have been performing an increasing number of tasks at video display terminals (VDTs) without leaving their desks; as a result, VDT users have become more susceptible to inadequate workplace equipment and conditions, and constrained or improper postures. Recently, in the office, there has been a significant increase in the number of injuries due to over-exertion, and repetitive strain. Many of these injuries are associated with the use of the VDT. This standard is based on the Canadian Standards Association (CSA) Standard Z412-M89 and on widely accepted "best practices guidelines" which are considered prudent practice for the avoidance of ergonomic-related injuries and losses.

Scope
Definitions
Responsibilities
    Departments/Faculties
    Workers
Office Ergonomics Requirements for Moderate and Intensive Computer Users
    Office Chairs
    Computer Work Stations
    Computer Accessories
    Lighting
    Posture and Work Habits for Moderate/Intensive Computer Users
    Comments Regarding the Use of Laptops
 

SCOPE:

This standard applies to Departments/Faculties in which individuals perform moderate and/or intensive computer work.

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DEFINITIONS:

moderate computer user: an individual who regularly uses the computer between 3 and 5 hours per day

intensive computer user: an individual who regularly uses a computer for more than 5 hours per day

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RESPONSIBILITIES:

Departments/Faculties shall:

OFFICE ERGONOMICS REQUIREMENTS FOR MODERATE / INTENSIVE COMPUTER USERS:

Office Chairs

Chairs are a crucial component of the office environment. A good adjustable chair can assist computer users to work comfortably and to accommodate the work surface and tasks performed.

Chairs should have the following features:

• seat height  must adjust to allow the user to place the feet firmly on the floor or a supportive footrest;
  - assuming an adjustable work surface height, an adjustment range of 380-520 mm (15 - 20.5") will allow 90% of potential users to find a comfortable sitting height while wearing shoes

• seat pan depth must be such that the user can maintain contact with the backrest in the lumbar area and avoid increased pressure on the back of legs and behind the knees;
  - seat pan depth should be less than 430 mm (17") and there should be space, about the width of a clenched fist, between the front of the seat pan and the back of the knees
  - horizontal adjustment of the backrest is an excellent feature to permit changing the effective seat pan depth - a good range of seat pan depth is 380-430 mm (15" - 17") -- a backrest like this will permit all but the shortest 5% of users to have adequate back support while seated;
• the seat pan should have a "waterfall" or rounded front edge to minimize pressure on the back of the legs;

• backrest should provide good contact and support for the lumbar region of the user's back;
  - the backrest should be vertically adjustable
  - the backrest should have a height of 380-540 mm (15-21") and a width of 350-480 mm (14-19")
  - the backrest tilt angle may be fixed, adjustable or spring-tensioned; if fixed, an angle of 103 +/- 1 degrees is suitable; if adjustable , a range of 95-110 degrees is usually sufficient; the force of a spring-tensioned reclining backrest should be adjustable to suit the user's needs;
• adjustable armrests (adjustable in both the horizontal and vertical planes) which can provide light arm support are recommended for moderate and intensive computer users -- armrests should not impede access to the work station or arm movement however;

• five-pronged chair base with casters for stability and easier mobility;
  - the ability to swivel 360 degrees and move the chair around improves access to work materials, eases sitting down and standing up and reduces twisting stresses on the spine;
  - appropriate casters for the surface (hard casters for soft floors or soft casters for hard floors);
• seat cushion should have minimal contouring to allow easy shifting of position and there should not be any local pressure points such as buttons or prominent seams

Computer Work Stations

•  the work surface should be chosen to complement the task being performed and be able to accommodate the tools and space required;
   
• moderate and intensive computer users should sit directly in front of the monitor and keyboard/mouse;
  - lateral viewing boundaries should not exceed 30 degrees either side of the body centre-line
• the mouse or pointing device should be located next to the keyboard (as close as possible and at the same height) to minimize reach;
   
• the keyboard and mouse (or other pointing device) should be located at a height that allows the user's forearms, wrists and hands to be parallel to the floor (the surface of the keyboard should generally be lower than a typical writing surface in order to permit the best posture) (see Posture and Work Habits);
  - underdesk adjustable height keyboard/mouse arms should be used to accommodate this need when the work surface height cannot be altered to accommodate this posture
  - an adjustment range of 600-730 mm (24-29") will allow most people to adopt a suitable arm posture for repetitive keying; if a single fixed surface is used, a work surface height of 720 mm (~28") is commonly recommended
• work surface height should provide adequate clearance for the operator's legs when seated in his or her most comfortable sitting position;
   
• monitor viewing distance should be about arm's length away when seated comfortably in front of the keyboard;
   
• the computer screen should be positioned such that the top of the screen is about eye level or slightly lower (0 to 60 degrees below eye level is usually suggested);
  - individuals who wear bifocals and trifocals may need to place the monitor lower than this to maintain comfortable (neutral) neck posture

• a document holder should be available for supporting documents in roughly the same plane as the computer monitor;
  - depending on how a document is used, a document holder may be placed on either side of the computer monitor or it may be more effective if situated directly in front of the user, between the keyboard and monitor;
   
• a foot rest should be provided if feet cannot rest comfortably on the floor while seated at the work station;
   
• wrist or palm rests to help maintain straight wrist posture between keyboarding activities should be available on request -- these devices must not be actively used during keyboard/mouse work but rather to "rest" the wrists periodically;
   
• if the work surface cannot properly accommodate a keyboard/mouse and monitor (i.e. the surface is too high or too shallow) then an adjustable underdesk keyboard/mouse support device should be used;
   
• if the monitor is too low, equipment such as monitor risers or blocks should be used;
   
• if telephone use is a major component of the job (such as reception areas), especially in combination with computer work, a telephone headset should be provided;
  - for individuals for who do not use the telephone quite as much as that described above, a telephone handset attachment is an excellent alternative to minimize "crunching" the handset between the ear and shoulder;
   
• if glare is a problem that cannot be eliminated through other control measures, an anti-glare screen should be provided (see Lighting)

Lighting

•  lighting for computer work stations should be set up to minimize glare and visual discomfort
  - computer work requires lower overall light levels than paper-oriented desk work;
• glare from natural and overhead light sources on computer screens should be minimized as much as possible
  - position computer work stations between rows of overhead lights rather than directly below;

  - position computer work stations at right angles to windows (e.g. operator does not face window or have back to window);

  - utilize partitions to block light from windows and overhead lights;

  - ensure that windows have coverings such as venetian blinds or drapes so that light levels can be controlled;

  - request that the some of the overhead light bulbs be removed the vicinity of computer stations -- contact Facilities and Services or Physical Plant;

  - parabolic louvres, baffles or filters can help reduce glare;

  - tilt the monitor slightly downward to reduce reflection from overhead lights; and

  - use a good quality anti-glare filter on the monitor if necessary

Posture and Work Habits for Moderate / Intensive Computer Users

• keep the neck and shoulders relaxed, keep elbows in close to the waist and avoid "hunching" or raising the shoulders;
   
• the forearms, hands and wrists should be kept parallel to the floor and in a non-reaching position;
   
• when using a mouse or other pointing device, keep the device as close as possible and at the same height as the keyboard (to avoid excessive arm extension);
   
• when using a mouse device, avoid "planting" the wrist on the work surface and instead, use the large muscles in the upper arm to move the device;
   
• avoid applying excessive hit or grip force when keyboarding or using a pointing device;
  the top of the monitor screen should be at eye level or slightly lower;
   
• the monitor should be located about arm's length away when seated comfortably at the keyboard;
   
• when sitting in the chair, the thighs should be parallel to the floor with about a 90^o angle between the thighs and calves (there should also be space, about the width of a clenched fist, between the front of the chair and the back of the knees);
• the feet should be able to rest comfortably on the floor -- if this is not possible, a footrest must be used;
   
• ensure that the backrest of the chair is adjusted to provide good support, particularly for the lower back (lumbar area);
   
• the monitor and keyboard should be located directly in front of the operator;
   
• if documents or reference materials are used often at the computer, a document holder should be used;
   
• place frequently used items such as a telephone or files within easy reach and avoid frequent overhead reaches or situations that require twists and reaches behind the body;
   
• take frequent vision breaks by glancing away from the monitor and focussing on a distant object for 10-15 seconds for every 30 minutes of computer use;
   
• take a 5 minute "break" for every hour of keyboard/mouse activity -- a "break" could involve performing a non-computer related task such as filing, photocopying, returning phone calls, etc, or simply standing up to stretch, move around and change body posture.

  
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Laptop computers have several advantages for users in terms of being lightweight and highly portable, but these desirable design features present inherent ergonomic problems when these devices are used extensively by moderate and intensive computer users. Because the keyboard/pointer and the screen are attached, postural compromises are unavoidable. Short-term, infrequent use of laptops is not problematic but if a laptop is being used in one location for extended periods of time, then it is not the right tool for the job.   If a laptop needs to be used in one location regularly for any length of time, a separate monitor or keyboard and mouse should be provided at that location. In addition, moderate and intensive laptop computer users need to be very aware of their keyboarding posture (avoid bending and resting wrists on the edge of the laptop, for example).